Keep your engine cool with our guide to cooling systems

Getting to Know…

Your Car ’s
Air Conditioning and
Engine Cooling System

How the systems work
How to get optimum performance
How to recognize problems

Operation and Maintenance Tips
Page 24

All technical data, information and comments provided in this publication are done as a
public service to you as a reader of this publication of the Mobile Air Conditioning Soci-
ety (MACS). The information contained in this publication is designed solely to help per-
sons reading it to better understand the components of their motor vehicle. Since
conditions of its use are outside of MACS' control, MACS assumes no liability for the use
of such information or any damages incurred through its use or application. Nothing
contained in such information is to be construed as contractual or providing some form
of warranty on the part of MACS. MACS recommends that you rely on the skills of certi-
fied technicians in dealing with any specific problem with your motor vehicle.

TABLE OF CONTENTS

INFORMATION ON AUTOMOTIVE AIR CONDITIONING AND COOLING
SYSTEMS FOR VEHICLE OWNERS - ....................................................1

YOUR CAR’S COOLING SYSTEM............................................................1
Cooling System Components and Operation ............................................1
Water Pumps, Thermostats, and Coolant Flow ........................................2
Radiators ..................................................................................................2
Heater Cores ............................................................................................3
Engine Cooling Fans ................................................................................3
Another Issue Related To Engine Cooling Airflow ....................................4

THINGS THAT GO WRONG WITH COOLING SYSTEMS........................4
Radiators and Heater Cores......................................................................4
Water Pumps ............................................................................................4
Thermostats ..............................................................................................5
Engine Cooling Fans ................................................................................5
Air Dams and Spoilers ..............................................................................6
Hoses and Belts ........................................................................................6
Core Plugs ................................................................................................6

COOLING SYSTEM PREVENTIVE MAINTENANCE................................6

YOUR CAR’S AIR CONDITIONING SYSTEM ..........................................7
Automotive Air Conditioning System Components and Operation ............8
Specific A/C Systems Components ..........................................................8
Evaporators ..............................................................................................9
Compressors ..........................................................................................10
Condensers ............................................................................................10
Receiver/Driers ........................................................................................11
Accumulators ..........................................................................................12
Expansion Valves ....................................................................................13
Air Conditioning System Component Illustrations ..............................14,15
Orifice Tubes ..........................................................................................16
Interior Air Distribution Componentry ......................................................16

TABLE OF CONTENTS

REFRIGERENTS AND SYSTEM LUBRICANTS ....................................17
Refrigerant Types ....................................................................................17
Lubricant Types ......................................................................................18

A QUICK REVIEW ..................................................................................18
A Word About Automatic Temperature Control Systems ........................19

THINGS THAT GO WRONG WITH AUTO A/C SYSTEMS ....................19
with Evaporators: ....................................................................................19
with Compressors: ..................................................................................20
with Condensers: ....................................................................................20
with Receiver/Driers and Accumulators:..................................................21
with Expansion Valves and Orifice Tubes: ..............................................21
with Pipes, Hoses, Gaskets and Seals: ..................................................21
with Air Distribution Systems: ..................................................................21
A Final Word on Things that Go Wrong ..................................................22

ADDITIONAL SERVICE CONSIDERATIONS ........................................22

AUTOMOTIVE AIR CONDITIONING OPERATING MAINTENANCE TIPS ..24
To achieve the quickest interior cool down, perform the following steps: ....24
More Operating Tips ..............................................................................25
Conduct an underhood inspection periodically. Here’s what to look for: ......25
Finally, two related points: ......................................................................28

CUSTOMER QUESTIONAIRE............................................................29,30

Information On Automotive
Air Conditioning and Cooling Systems
For Vehicle Owners -
Brought To You By MACS Worldwide,
The Mobile Air Conditioning Society
The Mobile Air Conditioning Society (MACS) Worldwide is a non-profit trade as-
sociation and our mission is clear and focused--as the recognized global authority on
mobile air conditioning and heat transfer industry issues.
It is a mission we have been fulfilling for our growing global membership and the
industry since 1981 in the following ways:
• Providing training, education and compliance programs for the mo-
bile air conditioning and heat transfer industry.
• Providing a forum for exchange of trade information on a regional,
national and international basis.
• Facilitating business between all segments of the industry.
• Providing tangible value for members, such as product marketing,
promotion and affinity programs.
• Disseminating legislative, regulatory and trade information (includ-
ing data, current developments and training materials).
• Providing information on legislative and regulatory initiatives that af-
fect the industry and advocate for the industry to legislative bodies.

YOUR CAR’S COOLING SYSTEM
Proper air conditioning system operation is dependent on proper cooling system op-
eration. So we can’t give you information on your car’s air conditioning system before
giving you information on your car’s cooling system. As they say, first things first.

Cooling System Components and Operation
As complex as motor vehicles have be-
come in recent years, one system that still
remains relatively easy to understand, and
in many ways, unchanged for years now, is
the engine cooling system. All still contain
familiar components such as the radiator,
water pump, fan, thermostat, heater core,
and hoses. One major change that has Engine
taken place in recent years, however, is the
Cooling
fact that most vehicles now have cooling
fans that are driven by an electric motor
System

Mobile Air Conditoning Society 1

instead of belts, and only run when signaled to do so through an electrical switch
and/or temperature sensor and relay. On vehicles with computerized engine controls,
the engine control computer usually controls the operation of the electric fan motor.

Water Pumps, Thermostats, and Coolant Flow
The water pump is the heart of the cooling system. It circulates the coolant through
the engine, radiator and
heater core. These days,
certain vehicles (like some
SUVs, vans and most hy-
brids) often have more
than one water pump, and
the auxiliary pumps are
usually run by electric mo-
tors and controlled by a
computer.
The coolant picks up
heat generated in the en-
gine by flowing around the
cylinders. It also flows
Typical Coolant Flow
through passages in the
cylinder head around the very hot combustion chambers. Since an engine operates
best within a certain temperature range, the thermostat stays closed to prevent the
coolant from flowing out of the engine to the radiator until the coolant has reached
a minimum temperature. After the thermostat opens, the coolant passes to the radi-
ator, where it can give up its heat to the atmosphere. The radiator depends on air flow-
ing through it to help it transfer the heat to the atmosphere. The coolant then returns
to the engine, and the process begins again.

Radiators
A radiator has 2 tanks, one containing the inlet and one containing the outlet.
These tanks, which can be at the top and bottom or sides, are usually made of alu-
minum, brass, copper, or plastic (most newer vehicles use the plastic type). On most
vehicles with automatic transmissions, one of the
tanks contains an automatic transmission fluid
cooler which is connected to the transmission by
metal lines or pipes.
The radiator’s two tanks have a series of flat-
tened tubes that are connected to, and run be-
tween them. Attached between the tubes are
accordion-style cooling fins. The tubes and fins
are also usually made of aluminum, brass, or cop-

2 Mobile Air Conditioning Society

per. As the hot coolant flows through the radiator tubes, heat is transferred to the fins,
then dissipated to the cooler air outside the vehicle.

Heater Cores
The heater core is located inside the passenger compartment of the vehicle, quite
often very deeply buried inside or under the instrument panel, or behind some other
type of interior trim panel. Some SUVs and vans have two heater cores, a front and a
rear. Regardless of location, all heater cores look like mini radiators.
Hot coolant flows through the heater cores’ internal tubes, and air from
the blower fan moves through the heater core to warm the interior of
the vehicle.

Engine Cooling Fans
Many vehicles now have
electric cooling fans that do
not operate until necessary,
when the engine coolant tem-
perature climbs above a certain
point. The changeover to elec-
tric cooling fans essentially
came about for two reasons.
One is simply packaging, be-
cause of front wheel drive
(FWD) vehicles with trans-
versely mounted engines.
Of course, the radiator
must remain at the front of the
vehicle so air can pass through
it, but in FWD vehicles, the
front of the engine faces the side of the car. “Old style” fans were driven off belts and
pulleys mounted at the front of the engine; this is not feasible for a FWD car.
The second reason for the switch to electric cooling fans is efficiency. The use of
electric fans can provide better fuel economy, as the fan does not operate at all times.
This reduces the overall load on the engine during most driving
conditions. This is why even many rear wheel drive (RWD) vehi-
cles now use electric cooling fans.
However, many RWD vehicles (especially trucks) still use belt
driven engine cooling fans, and most of these are equipped with a
device called a thermostatic fan clutch. The thermostatic fan clutch
Mechanical allows the fan to spin with reduced force when full cooling de-
Fan mand is not needed. This also helps reduce load on the engine,
Clutch which improves fuel economy.


Another Issue Related To Engine Cooling Airflow
Over the last few years, due to trends in styling, many newer cars do not have con-
ventional grills up front. Very often, a closed panel resides, or the hood extends down
to where a grill would have been. But all vehicles still depend on air passing through
the radiator to provide engine cooling, and also for A/C system operation. So where
and how does the air enter on cars like this? In most cases, from underneath the front
of car. There will be openings close to the road surface that allow cooling air to reach
the radiator. And on many cars, there is a component that plays a very big part in
making sure the air is routed properly into the engine compartment. This component
is usually called an air dam or front spoiler. Air dams/spoilers are often integrated
parts of the car’s bodywork, and are mounted way down low beneath the front
bumper. They act like scoops to “grab” and direct the cooling air to the radiator and
A/C condenser as the car moves down the road.

THINGS THAT GO WRONG WITH COOLING SYSTEMS
Radiators and Heater Cores
There are usually only two problems that occur with radiators or heater cores: leak-
age from a seam or hole in one of the tubes, or internal blockage. Blockage in the
cooling system most often occurs due to poor or infrequent maintenance. This illus-
trates the importance of following the vehicle manufacturer’s recommendations con-
cerning cooling system service intervals. A blockage often requires replacement of a
radiator, although some can be cleared. Radiators must also be kept clear externally of
leaves and other debris. Of course, radiators can be, and often are, damaged because
of a collision.
Many times, radiator leaks can be repaired, but these days, leaking radiators are
more often just replaced with new ones. Replacement is usually the more cost-effec-
tive repair, especially in the long run.
Leaking or blocked heater cores are generally not repaired, since they are usually
relatively inexpensive items. However, due to accessibility issues, a heater core re-
placement job is often extremely time consuming, and therefore costly, due to the
amount of labor involved.

Water Pumps
The same can be said about water pump replacement. Usually, the pump itself is
relatively inexpensive, but many times numerous other components must be removed
in order to be able to change one. This, of course, adds time and cost to the repair.
When a water pump fails, it is usually due to a leak caused by a worn bearing. The
bearing wears out, allowing the shaft to wobble, which damages the precision seal, re-
sulting in leakage. A water pump bearing can also fail due to a lack of, or loss of lu-


brication. This can particularly be a problem on engines where the water pump is
driven by the timing belt. Water pump seizure can cause the timing belt to suddenly
break, and on many engines this can cause severe internal engine damage, such as
bent valves and broken pistons.
A part inside the water pump, called the impeller, also sometimes fails or suffers
corrosion. This can prevent the pump from circulating the engine coolant properly,
which can lead to an engine overheating condition, or poor heater output inside the
vehicle.

Thermostats
Thermostats open and close with changes in engine temperature, and sometimes
become stuck. If stuck open, the engine never warms up properly and there is little or
no heat from the heater. A stuck-open thermostat can also cause poor fuel economy.
Stuck closed, a failed thermostat can cause engine overheating because the coolant
is never circulated to the radiator. A thermostat replacement is usually a pretty straight-
forward job, but thermostats may be in somewhat inaccessible locations on some cars,
adding to the degree of difficulty during replacement.

Engine Cooling Fans
Electric cooling fans are generally
reliable, but sometimes may fail to
activate due to an inoperative or de-
fective thermostatic switch, sensor or
relay. This may cause the engine to
overheat. Diagnosing a failure of this
type can sometimes be time consum-
ing, and also require special elec-
tronic diagnostic tools. Engine
Thermostatic fan clutches can Cooling
and do simply wear out over a period Fans
of time. This problem may not even
be noticeable however, until the ve-
hicle is subjected to some type of se-
vere operating condition, such as
towing, driving in extremely hot
weather, etc., as the fan still spins, Engine
even with a defective or marginally Driven Fan
operating clutch, just not as force-
fully as it should. Your service tech-
nician can perform tests to determine
if your fan clutch is operating properly.


Air Dams and Spoilers
Due to their very low mounting location, air dams and spoilers are often damaged
or even torn off completely if the car hits a parking bumper or curb. If this should
occur, proper airflow can become disrupted, and the engine and/or A/C system may
not cool properly. Or even worse, the engine may overheat. This is one more thing to
keep in mind if you experience an engine cooling or A/C performance problem.

Hoses and Belts
The cooling system hoses and belts can deteriorate over a pe-
riod of time. The hoses can develop leaks; the belts can crack,
shred, glaze and/or break. For this reason, a pressure check of the
cooling system should be performed at least once a year, and a vi-
sual inspection made to spot any impending belt problems. These
checks can indicate a potential failure before a breakdown occurs.

Core Plugs
There is one other component in cooling systems that bears mention: core plugs
(often referred to as freeze plugs). These metal discs are used to seal holes left in an en-
gine block or cylinder head from the manufacturing process. Over a period of time,
they can corrode and leak. Core plugs, because of accessibility issues, are sometimes
difficult to reach, and therefore time consuming to replace.

COOLING SYSTEM PREVENTIVE MAINTENANCE
As stated previously, regular inspections and pressure tests of your cooling system
are of utmost importance, as is good maintenance by following the vehicle manufac-
turer’s recommended coolant change intervals. As time passes, the protective anti-cor-
rosive additives in the antifreeze break down and lose their effectiveness. But antifreeze
has two other very important jobs as well:
• It is used to decrease the temperature at which the coolant
freezes.
• It is used to raise the temperature at which the coolant will begin
to boil.
It is also very important that the proper ratio of water
to antifreeze is always maintained. Unless specified oth-
erwise by the vehicle manufacturer, the coolant in most
vehicles should consist of a mixture of 50% water and
50% antifreeze before being added to the cooling sys-
tem. This 50/50 solution not only prevents freezing, but
also preserves proper cooling properties.
Also concerning the antifreeze to water mixture ratio:
adding more antifreeze to the mix (once again, unless


otherwise specified by the vehicle manufacturer) to increase its percentage in the mix-
ture is not better. Generally speaking, after the ratio exceeds more than about 65% an-
tifreeze to 35% water, freeze protection can actually diminish, but even worse, heat
dissipation can radically decrease, since the water is the primary substance used for this
purpose. Antifreeze itself actually has fairly poor heat transfer characteristics. Having
too much antifreeze in the mixture can actually cause engine overheating.
One more very important point about antifreeze: there are now many different
formulations available for use in different vehicles, and even in specific applications.
It’s not just “the green stuff ” any more, there’s red, orange, yellow, blue, etc. But don’t
think this means that you can just go by color. Even though color can be indicative
of a certain type of antifreeze, those of the same or similar color can be formulated sub-
stantially differently. For the most part, different types of antifreeze should not be
mixed, and also, in many cases, one type can not be substituted for another. Doing so
could cause all sorts of problems, including severe cooling system or engine damage.
Make sure that the proper antifreeze formulation for your vehicle is the one being
used. The vehicle manufacturer’s recommendation can be found in your owner’s man-
ual.
Regular maintenance is always the best insurance against cooling system failures,
and breakdowns on the road.

YOUR CAR’S AIR CONDITIONING SYSTEM
While it’s standard equipment on most cars
today, in the past, one of the most popular op-
tions selected at new car buying time was air
conditioning (A/C). While it was often one of
the more expensive options available, most ve-
hicle owners would admit that its initial pur-
chase price was a relative bargain in relation to
the long term comfort it provided.
Since the early days of automotive A/C,
many changes have taken place in the way the
systems operate, the A/C system components
and their designs, and of course, also in system
performance and efficiency. But perhaps more
importantly, starting in the early 1990s, other changes took place concerning how au-
tomotive A/C systems must be serviced, what they must be serviced with, and even
who is authorized to perform these services.
Let’s start with a brief description of A/C system components, and along the way,
we’ll explain how they work with the refrigerant to remove heat and humidity from
the passenger compartment of a vehicle. We’ll wrap up with information about the
A/C system service procedures mandated by the U.S. EPA.


Automotive Air Conditioning System Components and Operation
While in years past there were some differences, today, most automotive A/C sys-
tems contain 5 major components. These are the evaporator, compressor and con-
denser, and two other items, either a receiver/drier and expansion valve (also called a
thermal, or thermostatic expansion valve, or TXV for short), or an accumulator and
orifice tube; which two of these four last items depends on the type of A/C system.
Automotive A/C systems also contain “minor” components, such as rubber hoses
and metal piping (sometimes referred to as the “lines”), the air routing ductwork and
controls, and also electrical devices such as relays, switches, electronic control units,
etc. These additional components will vary by system and vehicle manufacturer.
Vehicles equipped with Automatic Temperature Control (ATC) also have a com-
puter that handles the ATC system functions. And speaking of computers, on most
vehicles equipped with computerized engine control systems (most since the early
‘80s), the engine control computer usually has some authority concerning A/C system
operation. There may even be other computers having a role in A/C system operation;
it all depends on the vehicle. In any case, even though the engine control computer,
or others, may not “directly be” air conditioning system components, they must be
taken into consideration during any discussion of A/C system operation, as their pres-
ence can have a great affect on A/C system service and diagnostic issues.

Specific A/C Systems Components
Before we begin our discussion of specific components, we must make two simple
statements:
1. When the pressure of a gas or liquid in a sealed system is raised,
the temperature of the gas or liquid also increases. Conversely, when
the pressure of a gas or liquid in a sealed system is lowered, the tem-
perature of the gas or liquid decreases. But it works both ways; when
the temperature of a gas or liquid in a sealed system is raised, the
pressure of the gas or liquid increases; when the temperature of a gas
or liquid in a sealed system is lowered, the pressure of the gas or liq-
uid decreases.
2. Just like other types of air conditioning and refrigeration systems,
an automotive A/C system has two distinct “sections;” the cool,
low-pressure section, and the warm, high-pressure section.
The reason we’ve kicked off our discussion on specific components with those two
statements will become apparent as we continue.
To make much of this easier to understand, we’re going to draw a comparison be-
tween A/C system components and engine cooling system components. Very often,
they work in a similar fashion, and most people already have at least some knowledge
concerning how engine cooling systems work.


Evaporators
The evaporator, also sometimes referred
to as the evaporator core, is one of the two
(maybe three) heat exchangers in a mobile
A/C system. In a typical passenger car or
pickup truck, the evaporator is usually lo-
cated inside the passenger compartment,
quite often deeply buried in or under the in-
strument panel. Some vehicles, usually vans
or SUVs, have two evaporators; one under
the instrument panel, or elsewhere at the front of the vehicle, and another one lo-
cated in or toward the rear of the vehicle. The rear evaporator is often located behind
a side panel or in the ceiling above the rear passengers.
Evaporators are usually made of aluminum. They look like, and in fact are, simi-
lar to radiators, only thicker and smaller in overall size. Like radiators, evaporators
consist of a series of internal tubes or “flow paths” with fins attached to them. Air can
pass freely through the fins, just like a radiator. But unlike a radiator, where the internal
tubes carry moving engine coolant, the passages in the evaporator carry moving re-
frigerant. When many people talk about refrigerant, they refer to it by its most pop-
ular brand name from years back, “Freon,™” or R-12. In the United States,
Freon™/R-12 was the type of refrigerant used in mobile A/C systems until about
1994, but it was replaced with a different refrigerant in all vehicles after the 1995
model year. The new refrigerant is HFC-134a (or R-134a).

But getting back to the term heat exchanger, what does that mean?
In a mobile A/C system, cold, low-pressure liquid refrigerant enters the evapora-
tor. Warm air from the interior of the vehicle passes through the evaporator by action
of the blower fan. Since it’s a fact of nature that heat always travels from a warmer area
to a cooler area, the cooler refrigerant flowing inside the evaporator absorbs heat from
the warm air. At the same time, humidity in the air condenses on the cool evapora-
tor’s surface, then eventually drips out of a drain tube to outside the vehicle (think of
how moisture forms on a cold bottle of soda pop on a humid day and forms a pud-
dle on your kitchen counter). This is why you see water dripping underneath a car
while the air conditioner is on. After the (now slightly warmer) refrigerant has com-
pleted its path through the evaporator, it moves on to the compressor.
So, as you can see, air conditioning does not actually cool the interior of the vehi-
cle. What it really does is remove heat and humidity from it.
The evaporator can be somewhat compared to a heater core working in reverse:
• Both are located inside the passenger compartment, often in very
close proximity, or even inside the same housing under the dash-
board.
• The heater core has hot engine coolant flowing through it, bring-


ing heat from the engine into the interior of the vehicle, where it is
distributed by the blower fan.
• The evaporator has cool refrigerant flowing through it, which
absorbs passenger compartment heat as the blower fan moves the
warm air across it.

Compressors
The compressor is a pump that moves
the refrigerant through the system. The re-
frigerant is carried by hoses and pipes from
one component to another. Compressor de-
signs vary, but they all essentially work the
same way.
The compressor is belt-driven by the en-
gine through an electromagnetic clutch (al-
though some hybrid vehicles use an electric motor to operate the compressor). The
clutch allows the compressor to disengage when the A/C is switched off, or at times
during A/C system operation when compressor function is not called for. The clutch
usually receives its electrical signal from a component called a relay, which in turn, re-
ceives its activation signal, in most cases, from the fuel injection or engine control
computer.
Besides pumping the refrigerant, the compressor has another job; at a certain point
in the system, it raises the pressure of the refrigerant from low to high, and as the re-
frigerant’s pressure goes up, so does its temperature. Raising the refrigerant’s pressure
and temperature enables it to release the passenger compartment heat it absorbed
while inside the evaporator. The heat release process takes place in the next compo-
nent to be discussed, the condenser.
The compressor can somewhat be compared to the water pump in an engine cool-
ing system:
• The water pump circulates the engine coolant throughout the
system. The coolant absorbs heat from the engine, and the water
pump moves it to the radiator where it releases the heat to the at-
mosphere. It also circulates hot coolant through the heater core to
warm the interior of the vehicle.
• The compressor circulates the refrigerant through the system.
The refrigerant absorbs the heat inside the vehicle while passing
through the evaporator. The refrigerant is then passed on to the
condenser, where it gives up the heat to the atmosphere.

Condensers
The condenser is the other heat exchanger in a mobile A/C system. Nowadays,
condensers are usually made of aluminum, but in the past, some were made of cop-


per/brass. Condensers look very much
like radiators, just a little thinner, and
since they also depend on air flowing
through them, are usually located in
front of the radiator.
Like radiators and evaporators, con-
densers are also constructed as a series of
tubes with fins around them. But unlike
an evaporator, whose job is to absorb
heat, the condenser’s job is to release
heat. More specifically, to release the heat
the refrigerant absorbed while it was flowing through the evaporator, very much the
same way the radiator releases the heat from engine coolant that the coolant absorbed
while it was flowing through the engine. The refrigerant enters the condenser as a
high-pressure vapor, but as it flows through the condenser and cools, it turns back
into a cooler high-pressure liquid.
The condenser can be compared to a radiator in an engine cooling system:
• The radiator releases heat from the hot engine coolant passing
through it, to the atmosphere.
• The condenser releases heat from the hot A/C system refrigerant
passing through it, to the atmosphere.

Receiver/Driers
Receiver/driers (also sometimes called “filter/driers” or “receiver/de-
hydrators”) look like small metal cans with an inlet and outlet. They are
only used in A/C systems that use expansion valves.
Receiver/driers are located in the high-pressure section of the sys-
tem, usually in the plumbing between the condenser outlet and the ex-
pansion valve inlet, although some may be connected directly to the
condenser.
Receiver/driers serve three very important functions:
1. They act as a temporary storage containers for oil and refriger-
ant when neither are needed for system operation (such as during
periods of low cooling demand). This is the “receiver” function of
the receiver/drier.
2. Most receiver/driers contain a filter that can trap debris that may
be inside the A/C system.
3. Receiver/driers contain a material called desiccant. The desiccant
is used to absorb moisture (water) that may have gotten inside the
A/C system during manufacture, assembly or service. Moisture can
get into the A/C components from humidity in the air. This is the
“drier” function of the receiver/drier.


Damage can occur if there’s excessive moisture inside an A/C system. It can cause
corrosion, as well as possibly degrade the performance of the compressor’s lubricating
oil.
The receiver/drier should be replaced any time the system is opened for service, and
most compressor warranties require it. The desiccant is only capable of absorbing a cer-
tain amount of moisture, and when the inside of the system and/or the receiver/drier
are exposed to the atmosphere, the desiccant can become very quickly saturated from
humidity in the air. If this occurs, the desiccant is no longer effective, and will not pro-
vide future protection. Additionally, the filter inside the receiver/drier could be re-
stricted by debris that may have been inside the system. This could diminish refrigerant
and oil flow.

Accumulators
An accumulator is comparable in purpose
to a receiver/drier. It serves similar, but slightly
different functions. An accumulator is also a
metal cylinder, but differs from a receiver/drier
in these three ways:
1. An accumulator is considerably
larger than a receiver/drier, usually
around twice the volume.
2. The accumulator is connected to
the evaporator outlet, in the low-pres-
sure section of the system.
3. The accumulator’s primary func-
tion is to store liquid refrigerant that is
exiting the evaporator, to prevent it from reaching the compressor.
If liquid refrigerant were to enter the compressor, it could cause
damage, as the compressor is not designed to pump liquid, only
vapor.
Accumulators are only used on systems that contain orifice tubes. It is a charac-
teristic of orifice tube systems to have large amounts of liquid refrigerant leaving the
evaporator. In other words, unlike in expansion valve systems, where all or most of the
refrigerant turned into a vapor while passing through the evaporator, in orifice tube
systems, the refrigerant leaves the evaporator still as a liquid. The accumulator is the
component in which the refrigerant gets the opportunity to warm up and change
from a liquid to a vapor before being drawn back into the compressor
Like receiver/driers, accumulators also serve as a temporary storage containers for
oil when the oil is not needed by the system.
Lastly, accumulators also contain the system desiccant and a small filter, so com-
pared to receiver/driers, the same “rules of replacement” apply.


Expansion Valves
The expansion valve’s place in the system is at the evaporator
inlet. Like any other valve, its job is to control flow; in this case, the
amount of refrigerant entering the evaporator. Since system operat-
ing conditions vary (sometimes high cooling demand, sometimes
low cooling demand) it is necessary to be able to adjust the amount
of refrigerant entering the evaporator. For any given operating con-
dition, if we were to allow too much refrigerant to enter the evaporator, it would get
too cold, and the moisture collected on it could freeze. This would not allow the hot
interior air to pass through its fins, and the refrigerant flowing inside the evaporator
would not be able to absorb the heat from the air. This would eventually bring cool-
ing to a halt. If we were to allow too little refrigerant to enter the evaporator, there may
not be enough to properly absorb the interior heat, which would also result in inad-
equate, or no cooling. This process of varying refrigerant flow based on system cool-
ing demand is referred to as “metering” the refrigerant into the evaporator.
So how does the expansion valve know how much refrigerant to meter into the
evaporator, and how does it do it? First the “how it does it”, and it’s quite simple. Ex-
pansion valves contain a movable rod which travels up and down inside the valve. As
the rod moves up and down, it can open and close the passage inside the valve that
serves as the flow path for the refrigerant. The valve does not have to be fully opened
or fully closed at any given time. Its position can vary, or modulate, between the fully
opened and fully closed positions. Because of this, it can very accurately meter the
precise amount of refrigerant needed to meet any given cooling demand.
This internal passage inside the TXV is much smaller than that of the refrigerant
flow pipe that delivers the refrigerant to it. Because of this, as the refrigerant flows
through this passage, its pressure drops, and it becomes the low-pressure liquid we
referenced earlier. So as you can see, the expansion valve also serves as a “dividing line”
between the high and low pressure sections of the system.
Now the “how does it know how much” part. This is based on the evaporator’s out-
let temperature. The warmer the evaporator is, the more refrigerant flow needed, and
vice-versa. The expansion valve has a temperature sensing device called a sensing bulb.
The sensing bulb measures temperature at the evaporator’s outlet and sends a signal
to the movable rod inside the expansion valve. This signal corresponds to the amount
of refrigerant needed, the rod moves to the proper position, and the correct amount
of refrigerant enters the evaporator.
An expansion valve could somewhat be likened to the thermostat in an engine
cooling system:
• The thermostat controls the flow of coolant from the engine to
the radiator based on cooling system temperature.
• The expansion valve controls the flow of refrigerant entering the
evaporator based on evaporator temperature, or A/C system
load/cooling demand.


Orifice Tubes
Orifice tubes are used in systems that don’t use expansion
valves. Like an expansion valve, the orifice tube is used to con-
trol the amount of refrigerant entering the evaporator. The di-
ameter of the orifice tube is similarly small to that of the passage
inside the expansion valve, but there is one big difference between orifice tubes and
expansion valves. An orifice tube is a simple fixed device with no moving parts. It can-
not vary the amount of refrigerant flowing into the evaporator the way an expansion
valve can. So in systems that use orifice tubes, some additional method of refrigerant
flow control must be employed. Two of the most popular methods used to do this are
turning the compressor on and off at appropriate times, or cycling it, or installing a
valve inside the compressor that can actually cause an adjustment to the pumping ca-
pacity of the compressor. This, of course, regulates the amount of refrigerant leaving
the compressor.

Orifice tubes also serve as a dividing line between the high and low pressure sec-
tions of the system.

Interior Air Distribution Componentry
Inside your vehicle, beneath the
instrument panel, there is a unit re-
ferred to by different names de-
pending on the vehicle
manufacturer, but often referred to
by the generic names “the plenum
assembly” or “the case/duct assem-
bly.” This unit contains a number
of different components which are
used to control the air routing and
distribution inside the vehicle,
based on the selected control panel
settings. It usually also contains the parts used to control the temperature of the dis-
charge air. The heater core and evaporator are usually contained within this assembly.
If the vehicle is equipped with a cabin air filter, most of the time it also will be located
in the plenum/case/duct assembly.
Inside the case/duct assembly are doors or flappers which can change position to
either expose or block airflow to and from various passages inside the case. These pas-
sages carry the forced air from the blower fan to either the dash outlet vents, floor
outlet(s), the windshield defrost outlet(s), or a combination of these. The doors may
be moved by simple cables, devices called vacuum motors (which use vacuum gener-
ated by the engine to cause movement), or small electric motors.


Refrigerants and System Lubricants
Refrigerant Types
Vehicle manufacturers have used two different refrigerants in automotive A/C sys-
tems. Most pre-1994 model year vehicles used CFC-12 (also called R-12; most peo-
ple know it by its most popular brand
name, Freon™). 1995-up model year
vehicles use HFC-134a, also referred to
as R-134a. Many (but not all) older sys-
tems that were designed to operate with
CFC-12 can be retrofitted to use HFC-
134a.
Even though there are a number of
refrigerants on the market listed as ac-
ceptable for use in automotive A/C sys-
tems by the U.S. EPA, only the two
mentioned above are approved by vehi-
cle manufacturers. Further, there is only
one refrigerant approved by all vehicle
manufacturers for use when retrofitting CFC-12 systems: HFC-134a. Lastly, HFC-
134a systems are not designed to operate with any other refrigerant other than HFC-
134a.
You must know that there is definitely a difference between what the EPA says
about retrofitting from an environmental standpoint, and what the vehicle manufac-
turers specify concerning retrofitting from a system performance and durability stand-
point.
SNAP is an acronym that stands for Significant New Alternatives Policy. This is the
program that the EPA has in place to describe refrigerants that have been submitted
to them for evaluation and acceptance for use as substitutes for CFC-12. The EPA
does not test the refrigerants; it relies on data submitted by the refrigerant manufac-
turers. The EPA evaluation concerns only environmental impact, health and safety.
The EPA does not evaluate a refrigerant’s A/C system performance or what effect it
may have on the long term durability of systems. If a refrigerant is listed as acceptable
by the EPA, it can legally be used in a mobile A/C system (subject to certain use con-
ditions). EPA acceptance of a refrigerant does not in any way guarantee it will provide
good system performance or long term durability.
For more information on the EPA accepted SNAP refrigerants, visit the EPA web
site www.epa.gov/ozone/snap/refrigerants/lists/chiller.html, or call the EPA’s Stratos-
pheric Ozone Protection Hotline, 1-800-296-1996.


Lubricant Types
A/C system lubricants are ones specifically made for use in A/C systems. The pur-
pose of these special oils is to provide lubrication for the compressor.
CFC-12 systems use mineral oil; all original equipment passenger car and light
truck HFC-134a systems use a synthetic lubricant called polyalkylene glycol, or PAG
for short. The switch to this type of oil was necessitated by the fact that mineral oil
does not serve as a suitable lubricant for use with HFC-134a. PAG is also specified by
the vast majority of vehicle manufacturers as the lubricant to use when retrofitting a
CFC-12 system to use HFC-134a.
There is one other type of synthetic lubricant marketed for use in automotive A/C
systems, called polyol ester, or POE or ester for short. This lubricant is specified by a
very few vehicle manufacturers for use when retrofitting certain models of their older
CFC-12 systems, but for no other applications.
Use of the correct (vehicle manufacturer approved) refrigerants and lubricants is
critical for proper system performance, durability, and longevity. Question your serv-
ice provider to make sure they are doing so!

A QUICK REVIEW
As a review, lets put it all together in one place, and once more trace the path of
the refrigerant starting at the evaporator outlet. For our example, we’ll use an expan-
sion valve type system equipped with a receiver/drier. (The process is similar in an
orifice tube/accumulator system.)


The compressor draws the heat-laden refrigerant vapor from the evaporator. It is
then compressed and sent under high pressure to the condenser. Since at this stage of
the cycle, the refrigerant is much hotter than the surrounding air, it gives up the heat
it absorbed in the evaporator to the cooler outside air flowing through the condenser
fins. As the refrigerant vapor gives up its heat, it changes back to a liquid inside the
condenser. The liquid refrigerant then moves into the receiver/drier, where moisture
it may contain is absorbed by the desiccant. Some refrigerant may also be temporar-
ily stored in the receiver/drier until it is needed in the evaporator, dictated by system
cooling demand. The liquid refrigerant leaves the receiver/drier, and is metered back
into the evaporator as a low-pressure liquid. The refrigerant picks up heat from the
warm interior air passing through the evaporator, and changes back into a vapor. The
warm air is moved through the evaporator, and cooled air circulated throughout the
interior of the vehicle, by the blower fan. The now-heated vapor travels to the evapo-
rator outlet, returns to the compressor, and the cycle begins again.

A Word About Automatic Temperature Control Systems
ATC systems contain many complex components, with comparably complex serv-
ice and diagnostic procedures, all beyond the scope of this publication.

THINGS THAT GO WRONG WITH AUTO A/C SYSTEMS
The upcoming section will help you gain an understanding of the types of failures
that can occur in automotive A/C systems, and procedures that may be necessary to
correct them.

Things That Go Wrong…
with Evaporators:
Evaporator failures can usually be summed up in one word: leakage. Leaks can
occur for a few different reasons. Usually, either a seam or weld has gone bad, cre-
ating a leak point, or corrosion has occurred, causing an “outside-in” failure. This
often happens because leaves or other organic material enter the evaporator case
through the exterior air intake vents and come in contact with the evaporator’s sur-
face. This moist atmosphere causes decomposition of the organic materials, and
can form caustic corrosive substances which can eventually perforate the surface of
the evaporator. These same substances can also sometimes lead to an odor problem
inside the vehicle, most noticeable when the system is first operated. Various de-
odorizing biocide treatments and drying modules are available to help with this
problem. The evaporator fins are also susceptible to clogging from leaves and other
debris.


Whichever the type of evaporator failure, it must be replaced. And while an
evaporator in and of itself may not be (for most vehicles) a very costly part, de-
pending upon its location (usually like heater cores, deeply buried beneath the in-
strument panel) this is often a very time consuming, and therefore costly repair.

with Compressors:
Compressors are generally reliable components, but can catastrophically fail
due to a lack of lubrication, just like your car’s engine. Lubricating oil can leave the
system if a refrigerant leak occurs, because the leaking refrigerant can carry lubri-
cant out with it. Such a failure can cause the compressor to lock up (seize) or wear
out prematurely. A catastrophically failing compressor can also load up the inside
of the A/C system (particularly the condenser) with debris, usually small chips of
metal.
A compressor can also fail because of too much oil in the system, which can
cause its internal valves to break. Compressors themselves may also develop a re-
frigerant leak, which usually necessitates their replacement.
Compressors may also be damaged by things such as an overcharge of refriger-
ant, excessive amounts of air in the system, the use of the wrong refrigerant or lu-
bricant, inadequate condenser airflow, or even engine cooling system problems.
And of course, just like any other component that contains moving parts, com-
pressors may sometimes fail simply due to wearing out or breakage.
Unlike in years past, with the exception of clutch replacement, compressors are
not generally serviced in the repair shop any longer.

with Condensers:
Like evaporators, condensers are also susceptible to external blockage, mostly
from things like leaves, insects, or even dust. A good cleaning with water, maybe
even using soap and a soft-bristle brush, often does a good job of clearing debris
from the outside of a condenser. But as previously mentioned, condensers are also
susceptible to severe internal blockage after a compressor failure. Metal particles
and other debris from the failing compressor move into the condenser with the re-
frigerant, and can quickly block the very small passages inside the condenser. In
some instances, it may be possible to flush this debris from inside the condenser,
but in many cases, the blockage is so severe that the condenser must be replaced.
Also like evaporators, condensers can suffer a seam or weld failure, resulting in
leakage. But condensers must contend with something that evaporators don’t; be-
cause of their “up front” mounting location, condensers can easily suffer physical
damage, from debris like small stones and such kicked up off the road, or from
front-end collisions.
In the vast majority of circumstances, internally clogged, leaking, or damaged
condensers are not repaired, but replaced with new units.


with Receiver/Driers and Accumulators:
Receiver/driers and accumulators rarely fail themselves, but as mentioned previ-
ously, need to be replaced whenever the system is opened for any other type of serv-
ice. When a failure does occur with a receiver/drier or accumulator, it is usually due
either to clogging from debris inside the A/C system (like from a failing or failed com-
pressor), or that the bag containing the desiccant has broken open, allowing desic-
cant material to circulate throughout the system with refrigerant and lubricant.
Sometimes, the desiccant material will disintegrate into small sand-like particles. This
can cause possible clogging in other system components.

with Expansion Valves and Orifice Tubes:
Expansion valves may fail in these three ways:
• Clogging or blockage
• Sticking either open or closed, or partially open or closed.
• Loss of proper metering ability due to wear, or an internal failure.
Of course, any of the above conditions could cause the wrong amount of refriger-
ant to be metered into the evaporator, which could lead to improper system operation.
Any of these problems will require replacement of the expansion valve.
An orifice tube is a very simple component with no moving parts. About the only
thing that ever goes wrong with them is clogging from debris, which always requires
orifice tube replacement.

with Pipes, Hoses, Gaskets and Seals:
Of course, hoses, gaskets and seals throughout the
system are prone to leakage over a period of time. Metal
tubing can suffer a rub through, cracking, or breakage.
Very often, failed hoses and/or metal tubing can be re-
paired, but many times replacement is required.

with Air Distribution Systems:
Case/duct systems have proven to be fairly reliable and relatively problem free.
Failures in this area will usually fall into the following categories:
• A binding, sticking or broken air routing door. (Sometimes for-
eign objects can fall down inside vents and cause problems like this.)
• Breakage of door control linkage mechanisms. These are often
made of plastic.
• A slipping or binding control cable.
• Vacuum motor diaphragms can develop leaks.
• Electric control motor can fail either electrically, or mechanically.
These motors contain gear drive assemblies that can wear out over


a period if time.
• Cabin air filter needs changing. These often neglected compo-
nents eventually become dirty and clogged. This can reduce airflow,
or even possibly stop it altogether.
Because of their location or limited working space, replacing some of the above com-
ponents can often be difficult or time consuming. And therefore (you guessed it) costly.

A Final Word on Things that Go Wrong
As with many other systems on today’s high-tech computer controlled automo-
biles, getting to the root of an A/C system problem is sometimes not a quick or easy
task. In some instances, thorough troubleshooting aided by complex information and
sophisticated test equipment will be necessary. If this situation should arise, your re-
pair shop may tell you that it could take them some time (with an associated labor
charge) to perform a proper diagnosis. Please be patient with your service provider if
and when this should occur. Allow them the time they need to find out why your
A/C isn’t keeping you cool.

ADDITIONAL SERVICE CONSIDERATIONS
A 1990 amendment to the
Clean Air Act has forever changed
How CFCs Deplete the way air conditioning systems are
The Ozone Layer serviced. It is believed that the re-
lease of CFC-12 to the atmosphere
is responsible for depletion of the
earth’s ozone layer. Depletion of the
ozone layer causes an increase in the
amount of ultraviolet sun radiation
reaching the earth’s surface. This in-
creased level of ultraviolet radiation
is believed to be causing increases in
cases of certain types of skin can-
cers, increases in the incidence of
cataracts, causing damage to crops,
increasing the formation of ground
level ozone (which causes smog),
and causing damage to sensitive
aquatic ecosystems. To meet the re-
quirements in Section 609 of the
Clean Air Act Amendments of
1990, all technicians working on


the refrigeration portion of
automotive air condition-
ing systems must be certi-
fied by an EPA approved
organization in Refrigerant
Recovery and Recycling
Procedures. MACS had the
first such program to gain
EPA approval, in Septem-
ber 1991.
It used to be a common
practice to just release re-
frigerant to the atmosphere
when an A/C system needed to be opened for service, as refrigerant was then inex-
pensive and thought to be environmentally benign. But releasing refrigerant to the at-
mosphere is no longer permitted, and is illegal. Since 1995, whenever a repair is
needed to an automotive A/C system that requires opening the refrigeration portion
of the system, the refrigerant must be recovered into a special machine. Before the re-
frigerant can be recharged back into a vehicle, it must be recycled (cleaned of impu-
rities). A separate recovery and/or recovery/recycling machine is required for each type
of refrigerant, and these machines can be quite costly. This is one of the reasons that
the cost of automotive A/C service has escalated in recent years.
Also gone are the days of just continuing to top off a slowly leaking system. While
there is currently no federal regulation prohibiting this practice, the source of the leak
should be determined, and the proper repair performed. Because of its effect on the
ozone layer, CFC-12 went out of production on December 31, 1995, and because of
dwindling supplies, its cost has skyrocketed. So, today,
it doesn’t make economic sense to just let refrigerant
slowly leak away. This also holds true for HFC-134a.
While not nearly as expensive as CFC-12, it still
makes no sense to let it continually leak from a sys-
tem.
As stated previously, the refrigerant that was cho-
sen by all vehicle manufacturers for use in new vehi-
cle production since about 1995 is HFC-134a.
HFC-134a is also the refrigerant chosen by all vehicle
manufacturers for use when retrofitting one of their
older CFC-12 systems. No other refrigerant has been
approved by any vehicle manufacturer for retrofit pur-
poses, or for use in any of their HFC-134a systems for
that matter. Most vehicle manufacturers have devel-
oped retrofit procedures that can be followed to allow
the use of HFC-134a in their vehicles originally de-


signed to use CFC-12. Adhering to their procedures will usually provide the best retro-
fitted system performance.
Because of the availability of the many different EPA accepted refrigerants that
may be used as substitutes for CFC-12, the very real possibility of refrigerant cross con-
tamination exists. The use of the wrong, or contaminated refrigerant can cause ex-
pensive damage to your vehicle. Question your A/C service technicians to be sure they
are following vehicle manufacturer approved service guidelines, and also using the
proper manufacturer approved refrigerants and lubricants.
As we’ve now seen, because of government regulation, the cost of air conditioning
services has, and will probably continue to rise. But, there is an upside to all of this.
As further technological developments take place, driven by regulations as well as
higher consumer expectations, automotive A/C systems will continue to improve in
performance and durability, and ultimately provide more cool comfort for you, the ve-
hicle owner.

AUTOMOTIVE AIR CONDITIONING OPERATING
AND MAINTENANCE TIPS
Here’s how to get the most from your vehicle’s air conditioning system; how to
achieve the best performance, and also how to maintain it to avoid failures.
To achieve the quickest interior cool down, perform the following steps:
1. If possible, leave the windows down slightly on hot sunny days.
Temperatures in a closed car can reach 140° F. and higher! An A/C
system works by removing heat, so the cooler the interior temper-
ature is to start with, the easier and faster it will be able to do its job.
2. When you first get in the car, roll all the windows completely
down, or even better, open the doors for a short period of time.
This helps the hot interior air to move out quickly.
3. When you first turn the A/C on, set the controls to “MAX”
and/or “REC”, and high blower. This moves the highest volume of
air, recirculates the already cooling air for even faster cool down,
and prevents hot outside air from entering. As soon as you are com-
fortable, switch the system to “NORM” or “OUTSIDE”, and the
lowest blower speed that still provides comfort. The lower the
blower speed, the colder the air from the system.
4. Applying window tint can help reduce interior temperatures. The
tint does not necessarily have to be dark to reflect sunlight away, as
some tints have a metallic substance within them for this purpose.
(Note: The application of window tinting products may not be legal
in some states or municipalities. Always check local regulations.)


More Operating Tips
Automatic Temperature Control systems operate differently than manual sys-
tems. Make sure you read the owners manual for your car to gain a full under-
standing of exactly how your particular system works. Generally speaking though,
to achieve as quick a cool-down as possible with most ATC systems, set the tem-
perature as low as it will go upon initial operation, then adjust up as necessary.
In most vehicles, when windshield defrost is selected, the A/C compressor is
automatically activated. This helps provide air that is more dehumidified to the
windshield, which will de-fog it faster and keep it that way. Some systems don’t
work this way, but have a separate switch that will turn the compressor on. If your
car is so equipped, don’t forget to switch the A/C on to achieve quicker de-fog.
A common customer complaint concerning A/C systems is that they sometimes
produce odors. These odors have been described as smelling like anything from
dirty socks to gym lockers. Operating the system in the “OUTSIDE” air mode
(not “REC”) as often as possible can sometimes help prevent or lessen this condi-
tion.
If your car is equipped with one, make sure you change your cabin air filter at
least as often as recommended by the vehicle manufacturer. Most vehicle manu-
facturers recommend that cabin air filters be changed at least every year or 15,000
miles, whichever comes first. Some specify even stricter change intervals. Check
your owner’s manual to find out how often your cabin air filter should be changed.
A dirty cabin air filter can reduce system airflow; if neglected, and allowed to be-
come completely clogged, airflow may stop entirely.

Conduct an underhood inspection periodically. Here’s what to look for:
1. Check that all A/C and cooling system component mounting
bolts or other attaching hardware appear to be tight, and that
none appear to be missing.
2. Check that the caps are installed on the A/C system service
ports. This keeps out dirt, and also provides a seal for the service
port.
3. With the engine running, check that the compressor clutch
engages when the A/C is switched on. If it doesn’t, this is usually
an indication of a low (or empty) refrigerant condition, or an
electrical problem. Also, listen for rapid clicking or cycling noises
at the compressor when the A/C is switched on. If this is hap-
pening, it could also be an indication of a low refrigerant charge
or some other problems. If this is the case, have the system
checked by your service technician. (Note: Some A/C systems
prevent compressor clutch engagement in low temperatures, typ-
ically at or below 40° F.)


Technician using an electronic refrigerant leak detector.

4. Also with the engine running, and the A/C compressor oper-
ating, then switched off, listen for knocking, tapping, rumbling,
or buzzing sounds in the vicinity of the compressor. These could
indicate a failing compressor or compressor clutch, and/or could
also indicate loose mounting hardware or a refrigeration system
problem.
5. Check all belts for cracks, wear, and glazing. Have them re-
placed at the first sign of any of these conditions. Also, belts can
stretch and loosen over a period of time, so check for this condi-
tion, as well as belts that vibrate while the A/C is on with the en-
gine running. This can be an indication of a belt that needs to be
tightened, or a defective automatic belt tensioner. (Note: Always
be extremely careful any time you’re under the hood while the
engine is running. Stay away from all rotating components with
your hands, clothing, and hair, and always wear eye protection
around a running engine.)
6. Examine all A/C and cooling system hoses for cuts, abrasion,
weak spots, and signs of leakage. Leakage from A/C system hoses
is often indicated by an accumulation of dirt and oil, particularly
at connections and fittings.
7. Check the radiator for signs of leakage, and also check the level
and cleanliness of the antifreeze/coolant.


WARNING: NEVER REMOVE THE PRES-
SURE CAP WHILE THE ENGINE IS EVEN
THE LEAST BIT WARM! SCALDING HOT
COOLANT CAN SPURT OUT AND CAUSE
SEVERE BURNS! ALWAYS ALLOW THE
ENGINE TO COOL BEFORE REMOVING
THE CAP!
You should have the radiator and cooling system inspected and serviced per the
vehicle manufacturer’s recommendations, which can be found in the vehicle
owner’s manual. This should insure that the engine will operate at the proper tem-
perature. An engine that runs too hot can be a cause of poor A/C system per-
formance, and may suffer a reduced life span. Believe it or not, an engine that runs
too cool can also wear out pre-maturely.
8. Make sure the radiator and condenser (the object in front of

the radiator that looks like another thinner radiator) are free of
any obstructions, such as leaves, insects, etc. This could impede
airflow through them, which can result in reduced A/C and cool-
ing system performance. If they are blocked or dirty, you can
rinse them clean with a garden hose. Also, make sure that the fins


on the condenser are straight and not flattened. If this is the case,
and they are not severely damaged, they can often be restored to
their original shape with a special tool.

Finally, two related points:

1. Make sure all air deflectors or front “spoilers” are in place if
your car is equipped with one (or was until it got knocked off by
a parking bumper). These often channel cooling air to and
through the condenser and radiator. Some cars may even over-
heat if these components are broken or missing
2. Car “bras” or bug screens may block airflow to the condenser
and radiator. Check to see if this will be the case if you intend to
install one. Even though it may not cause the car to overheat, it
could cause enough of a reduction in airflow to affect A/C system
performance.

Adhering to all of the above advice should keep you cool, prolong the life of
your car’s A/C and engine cooling systems, and also prevent surprise breakdowns.


AIR CONDITIONING HEATING CUSTOMER QUESTIONNAIRE
Now, MACS is bringing valuable information directly to you, the vehicle owner.
Read the following material carefully, as it will help you get the best possible per-
formance from your car’s A/C system. And if and when repairs are needed, this in-
formation will help you be an informed consumer.
CUSTOMER
Name ____________________________________________________

Phone ____________________ Date __________________________

Address __________________________________________________

City ______________________ State______ Zip ________________

VEHICLE Year ______________Make__________________________

Model ________________Color ______________________________
AlC System Type -
J Manual
J Auto. Temp. Control
J Dual/Rear Auxiliary Unit
PROBLEM / SYMPTOM
J No AlC
J No Heat
J No Defrost
J Poor Cooling
J Poor Heating
J Improper Fan/Blower Operation
J Air From Wrong Operation Outlet(s)
J No Temperature Control
J Noise Inside Car
J Noise Under Hood
J Interior Water Leak
J Engine Coolant Leak
J Warning Light(s) On
J Odor
J Other continued on reversed side

WHEN DOES THE PROBLEM OCCUR?
J Always
J Intermittent
J When Hot
J When Cold
J At Start Up
J During Warm Up
J At Idle
J High Engine Speeds
J Driving Away From Stop
J At Road Speeds

Have there been any previous attempts to repair this problem?
J No J Yes

If there were previous repair attempts, what was done? (What parts were
installed, etc.) ______________________________________________
______________________________________________________

Did previous repairs help the problem?
J No J Some J A lot J At first, but not now.

Have repairs or service of any kind been recently performed to the vehicle?
J No J Yes

If so, exactly what was done? __________________________________
________________________________________________________
________________________________________________________

*FURTHER DESCRIPTION OF THE PROBLEM
________________________________________________________
________________________________________________________


Copyright 2007, MACS Worldwide. All rights reserved. No part of this publication
may be reproduced in any form, in an electronic retrieval system or otherwise, without
the prior written permission of the publisher.

If you would like to order more of these booklets, please contact:
MACS Worldwide, P.O. 88, Lansdale, PA 19446, USA
Phone:(215) 631-7020 • Fax: (215) 631-7017 • Email:info@macsw.org.

See us on the web!
www.macsw.org

MACS Worldwide
P.O. 88, Lansdale, PA 19446, USA
Phone:(215) 631-7020 • Fax: (215) 631-7017 • Email:info@macsw.org.

See us on the web!
www.macsw.org

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