Macs Consumer Booklet

Getting to Know…

Your Car’s Air Conditioning and

Engine Cooling System

Operation and Maintenance Tips

Page 24

� How the systems work

� How to get optimum performance

� How to recognize problems

All technical data, information and comments provided in this publication are done as apublic 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 useof 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 formof 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 COOLINGSYSTEMS FOR VEHICLE OWNERS - ....................................................1

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

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

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

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

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

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

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

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

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

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

TABLE OF CONTENTS

Information On AutomotiveAir Conditioning and Cooling SystemsFor 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 onmobile air conditioning and heat transfer industry issues.

It is a mission we have been fulfilling for our growing global membership and theindustry 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 SYSTEMProper 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 beforegiving you information on your car’s cooling system. As they say, first things first.

Cooling System Components and OperationAs complex as motor vehicles have be-

come in recent years, one system that stillremains relatively easy to understand, andin many ways, unchanged for years now, isthe engine cooling system. All still containfamiliar components such as the radiator,water pump, fan, thermostat, heater core,and hoses. One major change that hastaken place in recent years, however, is thefact that most vehicles now have coolingfans that are driven by an electric motor

EngineCoolingSystem

Mobile Air Conditoning Society 1

instead of belts, and only run when signaled to do so through an electrical switchand/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 FlowThe water pump is the heart of the cooling system. It circulates the coolant through

the engine, radiator andheater core. These days,certain vehicles (like someSUVs, vans and most hy-brids) often have morethan one water pump, andthe auxiliary pumps areusually run by electric mo-tors and controlled by acomputer.

The coolant picks upheat generated in the en-gine by flowing around thecylinders. It also flowsthrough passages in thecylinder head around the very hot combustion chambers. Since an engine operatesbest within a certain temperature range, the thermostat stays closed to prevent thecoolant from flowing out of the engine to the radiator until the coolant has reacheda 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 returnsto the engine, and the process begins again.

RadiatorsA 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 mostvehicles with automatic transmissions, one of thetanks contains an automatic transmission fluidcooler which is connected to the transmission bymetal 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 areaccordion-style cooling fins. The tubes and finsare also usually made of aluminum, brass, or cop-

2 Mobile Air Conditioning Society

Typical Coolant Flow

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 CoresThe 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 othertype 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 fromthe blower fan moves through the heater core to warm the interior ofthe vehicle.

Engine Cooling FansMany vehicles now have

electric cooling fans that donot operate until necessary,when the engine coolant tem-perature climbs above a certainpoint. The changeover to elec-tric cooling fans essentiallycame about for two reasons.One is simply packaging, be-cause of front wheel drive(FWD) vehicles with trans-versely mounted engines.

Of course, the radiatormust remain at the front of thevehicle so air can pass throughit, but in FWD vehicles, thefront of the engine faces the side of the car. “Old style” fans were driven off belts andpulleys 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 ofelectric 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 drivingconditions. This is why even many rear wheel drive (RWD) vehi-cles now use electric cooling fans.

However, many RWD vehicles (especially trucks) still use beltdriven engine cooling fans, and most of these are equipped with adevice called a thermostatic fan clutch. The thermostatic fan clutchallows the fan to spin with reduced force when full cooling de-mand is not needed. This also helps reduce load on the engine,which improves fuel economy.


MechanicalFan

Clutch

Another Issue Related To Engine Cooling AirflowOver 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 downto where a grill would have been. But all vehicles still depend on air passing throughthe radiator to provide engine cooling, and also for A/C system operation. So whereand how does the air enter on cars like this? In most cases, from underneath the frontof car. There will be openings close to the road surface that allow cooling air to reachthe radiator. And on many cars, there is a component that plays a very big part inmaking sure the air is routed properly into the engine compartment. This componentis usually called an air dam or front spoiler. Air dams/spoilers are often integratedparts of the car’s bodywork, and are mounted way down low beneath the frontbumper. They act like scoops to “grab” and direct the cooling air to the radiator andA/C condenser as the car moves down the road.

THINGS THAT GO WRONG WITH COOLING SYSTEMS

Radiators and Heater CoresThere 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 thecooling 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 aradiator, although some can be cleared. Radiators must also be kept clear externally ofleaves and other debris. Of course, radiators can be, and often are, damaged becauseof a collision.

Many times, radiator leaks can be repaired, but these days, leaking radiators aremore 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 usuallyrelatively inexpensive items. However, due to accessibility issues, a heater core re-placement job is often extremely time consuming, and therefore costly, due to theamount of labor involved.

Water PumpsThe same can be said about water pump replacement. Usually, the pump itself is

relatively inexpensive, but many times numerous other components must be removedin 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. Thebearing 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 isdriven by the timing belt. Water pump seizure can cause the timing belt to suddenlybreak, and on many engines this can cause severe internal engine damage, such asbent valves and broken pistons.

A part inside the water pump, called the impeller, also sometimes fails or sufferscorrosion. This can prevent the pump from circulating the engine coolant properly,which can lead to an engine overheating condition, or poor heater output inside thevehicle.

ThermostatsThermostats 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 orno 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 coolantis 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 FansElectric cooling fans are generally

reliable, but sometimes may fail toactivate due to an inoperative or de-fective thermostatic switch, sensor orrelay. This may cause the engine tooverheat. Diagnosing a failure of thistype can sometimes be time consum-ing, and also require special elec-tronic diagnostic tools.

Thermostatic fan clutches canand do simply wear out over a periodof time. This problem may not evenbe noticeable however, until the ve-hicle is subjected to some type of se-vere operating condition, such astowing, driving in extremely hotweather, etc., as the fan still spins,even with a defective or marginallyoperating clutch, just not as force-fully as it should. Your service tech-nician can perform tests to determineif your fan clutch is operating properly.


EngineCooling

Fans

EngineDriven Fan

Air Dams and SpoilersDue 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 shouldoccur, proper airflow can become disrupted, and the engine and/or A/C system maynot cool properly. Or even worse, the engine may overheat. This is one more thing tokeep in mind if you experience an engine cooling or A/C performance problem.

Hoses and BeltsThe 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 thecooling system should be performed at least once a year, and a vi-sual inspection made to spot any impending belt problems. Thesechecks can indicate a potential failure before a breakdown occurs.

Core PlugsThere 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 sometimesdifficult to reach, and therefore time consuming to replace.

COOLING SYSTEM PREVENTIVE MAINTENANCEAs 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 antifreezehas two other very important jobs as well:

• It is used to decrease the temperature at which the coolantfreezes. • It is used to raise the temperature at which the coolant will beginto boil.

It is also very important that the proper ratio of waterto antifreeze is always maintained. Unless specified oth-erwise by the vehicle manufacturer, the coolant in mostvehicles should consist of a mixture of 50% water and50% antifreeze before being added to the cooling sys-tem. This 50/50 solution not only prevents freezing, butalso 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, heatdissipation can radically decrease, since the water is the primary substance used for thispurpose. Antifreeze itself actually has fairly poor heat transfer characteristics. Havingtoo much antifreeze in the mixture can actually cause engine overheating.

One more very important point about antifreeze: there are now many differentformulations 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’tthink this means that you can just go by color. Even though color can be indicativeof 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 bemixed, and also, in many cases, one type can not be substituted for another. Doing socould 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 beingused. 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 carstoday, in the past, one of the most popular op-tions selected at new car buying time was airconditioning (A/C). While it was often one ofthe more expensive options available, most ve-hicle owners would admit that its initial pur-chase price was a relative bargain in relation tothe long term comfort it provided.

Since the early days of automotive A/C,many changes have taken place in the way thesystems operate, the A/C system componentsand their designs, and of course, also in systemperformance 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 evenwho 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 fromthe passenger compartment of a vehicle. We’ll wrap up with information about theA/C system service procedures mandated by the U.S. EPA.


Automotive Air Conditioning System Components and OperationWhile 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 athermal, or thermostatic expansion valve, or TXV for short), or an accumulator andorifice 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 hosesand metal piping (sometimes referred to as the “lines”), the air routing ductwork andcontrols, 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 mostvehicles equipped with computerized engine control systems (most since the early‘80s), the engine control computer usually has some authority concerning A/C systemoperation. 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 betaken 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 ComponentsBefore 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, whenthe 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; whenthe temperature of a gas or liquid in a sealed system is raised, thepressure of the gas or liquid increases; when the temperature of a gasor 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 twostatements 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 knowledgeconcerning how engine cooling systems work.


EvaporatorsThe evaporator, also sometimes referred

to as the evaporator core, is one of the two(maybe three) heat exchangers in a mobileA/C system. In a typical passenger car orpickup 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 vansor SUVs, have two evaporators; one underthe 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 behinda 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, evaporatorsconsist of a series of internal tubes or “flow paths” with fins attached to them. Air canpass freely through the fins, just like a radiator. But unlike a radiator, where the internaltubes 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 about1994, but it was replaced with a different refrigerant in all vehicles after the 1995model 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 actionof the blower fan. Since it’s a fact of nature that heat always travels from a warmer areato a cooler area, the cooler refrigerant flowing inside the evaporator absorbs heat fromthe 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 ofhow 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 carwhile 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 veryclose 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 isdistributed by the blower fan.• The evaporator has cool refrigerant flowing through it, whichabsorbs passenger compartment heat as the blower fan moves thewarm air across it.

CompressorsThe compressor is a pump that moves

the refrigerant through the system. The re-frigerant is carried by hoses and pipes fromone component to another. Compressor de-signs vary, but they all essentially work thesame 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). Theclutch allows the compressor to disengage when the A/C is switched off, or at timesduring A/C system operation when compressor function is not called for. The clutchusually 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 controlcomputer.

Besides pumping the refrigerant, the compressor has another job; at a certain pointin 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 pressureand temperature enables it to release the passenger compartment heat it absorbedwhile 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 thesystem. The coolant absorbs heat from the engine, and the waterpump moves it to the radiator where it releases the heat to the at-mosphere. It also circulates hot coolant through the heater core towarm the interior of the vehicle. • The compressor circulates the refrigerant through the system.The refrigerant absorbs the heat inside the vehicle while passingthrough the evaporator. The refrigerant is then passed on to thecondenser, where it gives up the heat to the atmosphere.

CondensersThe 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 muchlike radiators, just a little thinner, andsince they also depend on air flowingthrough them, are usually located infront of the radiator.

Like radiators and evaporators, con-densers are also constructed as a series oftubes with fins around them. But unlikean evaporator, whose job is to absorbheat, the condenser’s job is to releaseheat. More specifically, to release the heatthe refrigerant absorbed while it was flowing through the evaporator, very much thesame way the radiator releases the heat from engine coolant that the coolant absorbedwhile it was flowing through the engine. The refrigerant enters the condenser as ahigh-pressure vapor, but as it flows through the condenser and cools, it turns backinto 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 passingthrough it, to the atmosphere.• The condenser releases heat from the hot A/C system refrigerantpassing through it, to the atmosphere.

Receiver/DriersReceiver/driers (also sometimes called “filter/driers” or “receiver/de-

hydrators”) look like small metal cans with an inlet and outlet. They areonly 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 thecondenser.

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 duringperiods of low cooling demand). This is the “receiver” function ofthe receiver/drier.2. Most receiver/driers contain a filter that can trap debris that maybe inside the A/C system.3. Receiver/driers contain a material called desiccant. The desiccantis used to absorb moisture (water) that may have gotten inside theA/C system during manufacture, assembly or service. Moisture canget 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 causecorrosion, as well as possibly degrade the performance of the compressor’s lubricatingoil.

The receiver/drier should be replaced any time the system is opened for service, andmost 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/drierare exposed to the atmosphere, the desiccant can become very quickly saturated fromhumidity 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 refrigerantand oil flow.

AccumulatorsAn accumulator is comparable in purpose

to a receiver/drier. It serves similar, but slightlydifferent functions. An accumulator is also ametal cylinder, but differs from a receiver/drierin these three ways:

1. An accumulator is considerablylarger than a receiver/drier, usuallyaround twice the volume. 2. The accumulator is connected tothe evaporator outlet, in the low-pres-sure section of the system.3. The accumulator’s primary func-tion is to store liquid refrigerant that isexiting the evaporator, to prevent it from reaching the compressor.If liquid refrigerant were to enter the compressor, it could causedamage, as the compressor is not designed to pump liquid, onlyvapor.

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 theevaporator. In other words, unlike in expansion valve systems, where all or most of therefrigerant turned into a vapor while passing through the evaporator, in orifice tubesystems, the refrigerant leaves the evaporator still as a liquid. The accumulator is thecomponent in which the refrigerant gets the opportunity to warm up and changefrom a liquid to a vapor before being drawn back into the compressor

Like receiver/driers, accumulators also serve as a temporary storage containers foroil 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 ValvesThe 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, theamount of refrigerant entering the evaporator. Since system operat-ing conditions vary (sometimes high cooling demand, sometimeslow cooling demand) it is necessary to be able to adjust the amountof refrigerant entering the evaporator. For any given operating con-dition, if we were to allow too much refrigerant to enter the evaporator, it would gettoo cold, and the moisture collected on it could freeze. This would not allow the hotinterior air to pass through its fins, and the refrigerant flowing inside the evaporatorwould 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 maynot 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 theevaporator, 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. Asthe rod moves up and down, it can open and close the passage inside the valve thatserves as the flow path for the refrigerant. The valve does not have to be fully openedor fully closed at any given time. Its position can vary, or modulate, between the fullyopened and fully closed positions. Because of this, it can very accurately meter theprecise amount of refrigerant needed to meet any given cooling demand.

This internal passage inside the TXV is much smaller than that of the refrigerantflow pipe that delivers the refrigerant to it. Because of this, as the refrigerant flowsthrough this passage, its pressure drops, and it becomes the low-pressure liquid wereferenced 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, andvice-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 signalto the movable rod inside the expansion valve. This signal corresponds to the amountof refrigerant needed, the rod moves to the proper position, and the correct amountof refrigerant enters the evaporator.

An expansion valve could somewhat be likened to the thermostat in an enginecooling system:

• The thermostat controls the flow of coolant from the engine tothe radiator based on cooling system temperature. • The expansion valve controls the flow of refrigerant entering theevaporator based on evaporator temperature, or A/C systemload/cooling demand.


Orifice TubesOrifice 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 passageinside the expansion valve, but there is one big difference between orifice tubes andexpansion 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 expansionvalve can. So in systems that use orifice tubes, some additional method of refrigerantflow control must be employed. Two of the most popular methods used to do this areturning the compressor on and off at appropriate times, or cycling it, or installing avalve 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 leavingthe compressor.

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

Interior Air Distribution ComponentryInside your vehicle, beneath the

instrument panel, there is a unit re-ferred to by different names de-pending on the vehiclemanufacturer, but often referred toby the generic names “the plenumassembly” or “the case/duct assem-bly.” This unit contains a numberof different components which areused to control the air routing anddistribution 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 locatedin the plenum/case/duct assembly.

Inside the case/duct assembly are doors or flappers which can change position toeither 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, flooroutlet(s), the windshield defrost outlet(s), or a combination of these. The doors maybe 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 TypesVehicle 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 brandname, Freon™). 1995-up model yearvehicles use HFC-134a, also referred toas R-134a. Many (but not all) older sys-tems that were designed to operate withCFC-12 can be retrofitted to use HFC-134a.

Even though there are a number ofrefrigerants on the market listed as ac-ceptable for use in automotive A/C sys-tems by the U.S. EPA, only the twomentioned above are approved by vehi-cle manufacturers. Further, there is onlyone refrigerant approved by all vehiclemanufacturers 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 saysabout 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 theprogram that the EPA has in place to describe refrigerants that have been submittedto them for evaluation and acceptance for use as substitutes for CFC-12. The EPAdoes 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 itmay have on the long term durability of systems. If a refrigerant is listed as acceptableby 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 providegood system performance or long term durability.

For more information on the EPA accepted SNAP refrigerants, visit the EPA website www.epa.gov/ozone/snap/refrigerants/lists/chiller.html, or call the EPA’s Stratos-pheric Ozone Protection Hotline, 1-800-296-1996.


Lubricant TypesA/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 PAGfor short. The switch to this type of oil was necessitated by the fact that mineral oildoes not serve as a suitable lubricant for use with HFC-134a. PAG is also specified bythe vast majority of vehicle manufacturers as the lubricant to use when retrofitting aCFC-12 system to use HFC-134a.

There is one other type of synthetic lubricant marketed for use in automotive A/Csystems, called polyol ester, or POE or ester for short. This lubricant is specified by avery few vehicle manufacturers for use when retrofitting certain models of their olderCFC-12 systems, but for no other applications.

Use of the correct (vehicle manufacturer approved) refrigerants and lubricants iscritical 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 ofthe 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 anorifice tube/accumulator system.)


The compressor draws the heat-laden refrigerant vapor from the evaporator. It isthen compressed and sent under high pressure to the condenser. Since at this stage ofthe cycle, the refrigerant is much hotter than the surrounding air, it gives up the heatit absorbed in the evaporator to the cooler outside air flowing through the condenserfins. As the refrigerant vapor gives up its heat, it changes back to a liquid inside thecondenser. The liquid refrigerant then moves into the receiver/drier, where moistureit 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 systemcooling demand. The liquid refrigerant leaves the receiver/drier, and is metered backinto the evaporator as a low-pressure liquid. The refrigerant picks up heat from thewarm interior air passing through the evaporator, and changes back into a vapor. Thewarm air is moved through the evaporator, and cooled air circulated throughout theinterior 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 SystemsATC 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 failuresthat can occur in automotive A/C systems, and procedures that may be necessary tocorrect 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. Thisoften happens because leaves or other organic material enter the evaporator casethrough the exterior air intake vents and come in contact with the evaporator’s sur-face. This moist atmosphere causes decomposition of the organic materials, andcan form caustic corrosive substances which can eventually perforate the surface ofthe evaporator. These same substances can also sometimes lead to an odor probleminside the vehicle, most noticeable when the system is first operated. Various de-odorizing biocide treatments and drying modules are available to help with thisproblem. The evaporator fins are also susceptible to clogging from leaves and otherdebris.


Whichever the type of evaporator failure, it must be replaced. And while anevaporator 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 thesystem 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 wearout prematurely. A catastrophically failing compressor can also load up the insideof the A/C system (particularly the condenser) with debris, usually small chips ofmetal.

A compressor can also fail because of too much oil in the system, which cancause 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 arenot 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, maybeeven using soap and a soft-bristle brush, often does a good job of clearing debrisfrom the outside of a condenser. But as previously mentioned, condensers are alsosusceptible to severe internal blockage after a compressor failure. Metal particlesand 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. Insome 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 inleakage. But condensers must contend with something that evaporators don’t; be-cause of their “up front” mounting location, condensers can easily suffer physicaldamage, from debris like small stones and such kicked up off the road, or fromfront-end collisions.

In the vast majority of circumstances, internally clogged, leaking, or damagedcondensers 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 dueeither 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. Thiscan 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 onlything that ever goes wrong with them is clogging from debris, which always requiresorifice 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. Metaltubing 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 oftenmade 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 WrongAs 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 easytask. In some instances, thorough troubleshooting aided by complex information andsophisticated 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 laborcharge) to perform a proper diagnosis. Please be patient with your service provider ifand when this should occur. Allow them the time they need to find out why yourA/C isn’t keeping you cool.

ADDITIONAL SERVICE CONSIDERATIONS

A 1990 amendment to theClean Air Act has forever changedthe way air conditioning systems areserviced. It is believed that the re-lease of CFC-12 to the atmosphereis responsible for depletion of theearth’s ozone layer. Depletion of theozone layer causes an increase in theamount of ultraviolet sun radiationreaching the earth’s surface. This in-creased level of ultraviolet radiationis believed to be causing increases incases of certain types of skin can-cers, increases in the incidence ofcataracts, causing damage to crops,increasing the formation of groundlevel ozone (which causes smog),and causing damage to sensitiveaquatic ecosystems. To meet the re-quirements in Section 609 of theClean Air Act Amendments of1990, all technicians working on


How CFCs Deplete The Ozone Layer

the refrigeration portion ofautomotive air condition-ing systems must be certi-fied by an EPA approvedorganization in RefrigerantRecovery and RecyclingProcedures. MACS had thefirst such program to gainEPA approval, in Septem-ber 1991.

It used to be a commonpractice to just release re-frigerant to the atmospherewhen 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 isneeded to an automotive A/C system that requires opening the refrigeration portionof 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 typeof refrigerant, and these machines can be quite costly. This is one of the reasons thatthe 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. Whilethere is currently no federal regulation prohibiting this practice, the source of the leakshould be determined, and the proper repair performed. Because of its effect on theozone layer, CFC-12 went out of production on December 31, 1995, and because ofdwindling supplies, its cost has skyrocketed. So, today,it doesn’t make economic sense to just let refrigerantslowly leak away. This also holds true for HFC-134a.While not nearly as expensive as CFC-12, it stillmakes 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 vehiclemanufacturers for use when retrofitting one of theirolder CFC-12 systems. No other refrigerant has beenapproved by any vehicle manufacturer for retrofit pur-poses, or for use in any of their HFC-134a systems forthat matter. Most vehicle manufacturers have devel-oped retrofit procedures that can be followed to allowthe 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 thatmay 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 theyare following vehicle manufacturer approved service guidelines, and also using theproper manufacturer approved refrigerants and lubricants.

As we’ve now seen, because of government regulation, the cost of air conditioningservices 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 ashigher consumer expectations, automotive A/C systems will continue to improve inperformance and durability, and ultimately provide more cool comfort for you, the ve-hicle owner.

AUTOMOTIVE AIR CONDITIONING OPERATINGAND MAINTENANCE TIPS

Here’s how to get the most from your vehicle’s air conditioning system; how toachieve 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/Csystem 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 completelydown, 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 ofair, 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 thelowest blower speed that still provides comfort. The lower theblower speed, the colder the air from the system.4. Applying window tint can help reduce interior temperatures. Thetint does not necessarily have to be dark to reflect sunlight away, assome tints have a metallic substance within them for this purpose.(Note: The application of window tinting products may not be legalin 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 isautomatically activated. This helps provide air that is more dehumidified to thewindshield, which will de-fog it faster and keep it that way. Some systems don’twork this way, but have a separate switch that will turn the compressor on. If yourcar 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 sometimesproduce odors. These odors have been described as smelling like anything fromdirty 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 atleast as often as recommended by the vehicle manufacturer. Most vehicle manu-facturers recommend that cabin air filters be changed at least every year or 15,000miles, whichever comes first. Some specify even stricter change intervals. Checkyour 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 mountingbolts or other attaching hardware appear to be tight, and thatnone appear to be missing.2. Check that the caps are installed on the A/C system serviceports. This keeps out dirt, and also provides a seal for the serviceport. 3. With the engine running, check that the compressor clutchengages when the A/C is switched on. If it doesn’t, this is usuallyan indication of a low (or empty) refrigerant condition, or anelectrical problem. Also, listen for rapid clicking or cycling noisesat the compressor when the A/C is switched on. If this is hap-pening, it could also be an indication of a low refrigerant chargeor some other problems. If this is the case, have the systemchecked by your service technician. (Note: Some A/C systemsprevent compressor clutch engagement in low temperatures, typ-ically at or below 40° F.)



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 couldindicate a failing compressor or compressor clutch, and/or couldalso indicate loose mounting hardware or a refrigeration systemproblem.5. Check all belts for cracks, wear, and glazing. Have them re-placed at the first sign of any of these conditions. Also, belts canstretch 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 betightened, or a defective automatic belt tensioner. (Note: Alwaysbe extremely careful any time you’re under the hood while theengine is running. Stay away from all rotating components withyour hands, clothing, and hair, and always wear eye protectionaround 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 hosesis often indicated by an accumulation of dirt and oil, particularlyat connections and fittings. 7. Check the radiator for signs of leakage, and also check the leveland cleanliness of the antifreeze/coolant.

Technician using an electronic refrigerant leak detector.


WARNING: NEVER REMOVE THE PRES-SURE CAP WHILE THE ENGINE IS EVENTHE LEAST BIT WARM! SCALDING HOTCOOLANT CAN SPURT OUT AND CAUSESEVERE BURNS! ALWAYS ALLOW THEENGINE TO COOL BEFORE REMOVINGTHE CAP!

You should have the radiator and cooling system inspected and serviced per thevehicle manufacturer’s recommendations, which can be found in the vehicleowner’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 runstoo 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 ofany obstructions, such as leaves, insects, etc. This could impedeairflow through them, which can result in reduced A/C and cool-ing system performance. If they are blocked or dirty, you canrinse 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 totheir original shape with a special tool.

Finally, two related points:

1. Make sure all air deflectors or front “spoilers” are in place ifyour car is equipped with one (or was until it got knocked off bya parking bumper). These often channel cooling air to andthrough 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 condenserand radiator. Check to see if this will be the case if you intend toinstall one. Even though it may not cause the car to overheat, itcould cause enough of a reduction in airflow to affect A/C systemperformance.

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



AIR CONDITIONING & HEATING CUSTOMER QUESTIONNAIRENow, 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 - � Manual� Auto. Temp. Control � Dual/Rear Auxiliary Unit

PROBLEM / SYMPTOM � No AlC � No Heat� No Defrost� Poor Cooling � Poor Heating� Improper Fan/Blower Operation � Air From Wrong Operation Outlet(s)� No Temperature Control� Noise Inside Car � Noise Under Hood � Interior Water Leak� Engine Coolant Leak � Warning Light(s) On � Odor � Other continued on reversed side


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

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

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

______________________________________________________

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

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

If so, exactly what was done? __________________________________________________________________________________________________________________________________________________

*FURTHER DESCRIPTION OF THE PROBLEM________________________________________________________________________________________________________________

Copyright 2007, MACS Worldwide. All rights reserved. No part of this publicationmay be reproduced in any form, in an electronic retrieval system or otherwise, withoutthe 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, USAPhone:(215) 631-7020 • Fax: (215) 631-7017 • Email:[email protected].

See us on the web!www.macsw.org

MACS WorldwideP.O. 88, Lansdale, PA 19446, USA

Phone:(215) 631-7020 • Fax: (215) 631-7017 • Email:[email protected].

See us on the web!www.macsw.org

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