Prepare yourself for ASE testing with these questions on

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NOTE: The following questions are written in theASE style. They are similar to the kinds of questionsthat you will see on the ASE test, however, none ofthese questions will actually appear on the test.

1. Technician A says that evacuating an A/C system willremove air and moisture from the system. Technician Bsays that evacuating an A/C system will remove dirt par-ticles from the system. Who is right?

A. Technician A onlyB. Technician B onlyC. Both A and BD. Neither A or B

2. There is a growling or rumbling noise at the A/C com-pressor when the system is off and the engine is run-ning. The noise stops when the system is turned on.Technician A says that a bad compressor bearing couldbe the cause. Technician B says that a bad compressorclutch bearing could be the cause. Who is right?


3. The readings shown above are taken with the A/Csystem operating at an ambient (outside) temperature of85˚F (29˚C). What do the readings indicate?

A. normal operationB. low refrigerant levelC. a restriction in the high sideD. damaged compressor

4. Recovery/recycling equipment must have shutoffvalves located within 12-in. (30 cm) of the hoses’ ser-vice ends so that:

A. oil can be added to the refrigerantB. the unit can be isolated from the refrigerant

sourceC. the filter can be changed without discon-

necting the hosesD. refrigerant discharge can be kept to a minimum

5. When recovering refrigerant from an A/C system,how long should the technician wait after the recovery/recycling unit has been turned off to see if there is anyresidual pressure in the system?

A. 1 minuteB. 5 minutesC. 10 minutesD. 15 minutes

6. A system with a low pressure on the low side and aheavy frost accumulation on the inlet side of theThermostatic Expansion Valve (TXV) indicates a:

A. TXV stuck openB. clogged condenserC. defective compressorD. clogged screen or TXV stuck closed

7. A blower motor only works on high speed. Which ofthe following causes is the MOST LIKELY?

A. defective blower relayB. defective blower resistorC. defective blower switchD. blown fuse or tripped circuit breaker

8. A customer complains that when accelerating his carwith the A/C on, the cold air flow from the dash outletsshifts to the floor. Technician A says that this is causedby a faulty check valve in the vacuum reservoir.Technician B says that this condition is due to a vacuumleak. Who is right?


Prepare yourself for ASE testing with these questions onHEATING AND AIR CONDITIONING






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9. When pressure testing the cooling system on a latemodel gasoline engine vehicle, the pressure on thetester drops but no leaks can be found in the enginecompartment. Technician A starts the engine and, see-ing the pressure on the tester gauge increase, says thatthere is an internal leak, a blown head gasket.Technician B says that there cannot be an internal leakbecause the engine oil looks normal, not milky like itwould be if coolant were present, and there is no whitesmoke coming from the exhaust pipe. Who is right?


10. When identifying an A/C system, Technician A saysthat an accumulator located between the evaporatorand compressor is an indication that the system has anorifice tube. Technician B says that when the high-sideservice port fitting is smaller than the one on the lowside, the system uses R134a refrigerant. Who is right?


11. When troubleshooting an ATC system, the systemresponds when the ambient and in-vehicle temperaturesensors are heated and cooled. However, there is noresponse when the sunload sensor is exposed to a lightsource. Technician A says that the problem is with thesystem’s programmer. Technician B says that the prob-lem is with the sunload sensor. Who is right?


12. The following are all methods of orifice tube replace-ment EXCEPT:

A. Replace the line that incorporates the orificetube.

B. Disconnect the liquid line from the evapora-tor inlet line and pull the orifice tube straightout with an extractor tool.

C. Disconnect the liquid line from the evapora-tor inlet line and, using a twisting motion tobreak free of the line, pull out the orificetube with an extractor tool.

D. Cut out the section of line that contains theorifice tube and, using a kit, install a new ori-fice tube line segment.

13. When converting the A/C system in an older vehicleto R134a refrigerant, what percentage of the originalR12 charge amount should be used?

A. 75 percentB. 100 percentC. 99 percentD. 80-90 percent

14. A vehicle with R134a refrigerant in the A/C systemhas a refrigerant leak. Technician A says that a propanegas leak detector should be used to find the location ofthe leak. Technician B says that an electronic leak detec-tor should be used to check for leaks. Who is right?


15. Which of the following is a true statement regardingR134a refrigerant?

A. It is harmful to the ozone layer.B. It mixes with mineral oil.C. It requires a different desiccant than R12.D. It operates at lower pressures than R12.

16. The compressor in an A/C system does not run.When a jumper wire is used to connect the battery posi-tive terminal to the power connector, the compressorclutch engages. Technician A says that the clutch coil isdefective. Technician B says that the pressure cyclingswitch could be defective. Who is right?


17. The floor inside a vehicle is wet and there is a slimyfilm on the windows. Technician A says that the heatercore is leaking. Technician B says that the evaporatorcase drain plug is clogged. Who is right?


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18. During A/C system operation, a knocking sound canbe heard coming from the compressor. Technician Asays that there could be internal compressor damage.Technician B says that the compressor mounting brack-ets and bushings should be checked. Who is right?


19. All of the following could cause poor heater perfor-mance EXCEPT:

A. defective temperature blend door actuatorB. radiator coolant temperature below 150˚F

(66˚C)C. heater core return hose much cooler than

inlet hoseD. stuck open heater control valve

20. During an A/C system performance test, the air tem-perature at the center outlet duct is warm to slightly cooland the low and high-side pressures on the manifoldgauge set are both low. All of the following could be thecause of these symptoms EXCEPT:

A. clogged orifice tubeB. expansion valve stuck closedC. restricted receiver/drierD. plugged condenser

21. What is the minimum system pressure necessary toleak test with an electronic leak detector?

A. 25 psiB. 50 psiC. 75 psiD. 100 psi

22. Technician A says that when retrofitting an A/C sys-tem, the new R134a service ports are usually installedon the existing R12 fittings. Technician B says that if theold fittings are not converted, they should be labeled.Who is right?


23. When diagnosing an ATC system, most of the sys-tem temperature sensors can be tested for:

A. resistance and current flowB. resistance and voltage dropC. voltage drop and current flowD. current flow and continuity

24. During an A/C system performance test, high-sidepressure was found to be excessive and the A/C com-pressor continued to run. Technician A says that thehigh-pressure cutout switch could be defective.Technician B says that there could be an air flowobstruction at the condenser. Who is right?


25. The A/C compressor cycles rapidly, and air comingfrom the vents is only slightly cool. Technician A saysthe problem could be a low refrigerant charge.Technician B says the problem could be a defectivethermostatic switch. Who is right?


26. To properly evacuate an A/C system, the vacuumpump should be operated a minimum of:

A. 5 minutesB. 10 minutesC. 20 minutesD. 30 minutes

27. Technician A says that a special tool is required todisconnect and connect spring lock fittings. TechnicianB says that new when assembling spring lock fittings,new O-rings lubricated with clean refrigerant oil shouldbe used. Who is right?








28. All of the following are true statements concerningin-line filters EXCEPT:

A. They are usually installed in a system thathas suffered a compressor failure.

B. They are installed to protect the new com-pressor from metal chips or other debris thatcould be in the system from the originalcompressor failure.

C. They are installed to collect debris that couldclog the orifice tube or expansion valve filters.

D. Filters are only installed in the high side ofthe system.

29. Two technicians are discussing sight glass observa-tions. Technician A says that if foam is seen in the sightglass, the refrigerant charge is low. Technician B saysthat if oil streaks are seen in the sight glass, the refriger-ant charge is low. Who is right?


30. Technician A says that moisture in an A/C systemcan freeze in the expansion valve and stop the systemfrom cooling. Technician B says that moisture in the A/Csystem will react with R12 to form an acid that cancause corrosion. Who is right?


31. Low heater output can be caused by all of the fol-lowing EXCEPT:

A. an engine low on coolantB. a stuck open cooling system thermostatC. a restricted heater control valveD. a disengaged clutch type radiator fan

32. The high-side pressure in an A/C system is abovespecifications. All of the following could cause this prob-lem EXCEPT:

A. an overcharge of refrigerantB. restricted air flow across the condenserC. a slipping fan beltD. a broken compressor reed valve

33. When filling a container with recycled refrigerant, towhat percentage of the container’s gross weight ratingshould it be filled?

A. 50 percentB. 60 percentC. 70 percentD. 80 percent

34. A vacuum door actuator is being tested. When vac-uum is applied with a hand held vacuum pump, the doordoes not move and the reading on the vacuum gauge iszero. Technician A says that the door does not movebecause it is binding or obstructed. Technician B saysthat the door does not move because the actuator isdefective. Who is right?


35. A customer complains of a foul odor coming fromthe dash outlets whenever the A/C and blower are on.Technician A says that this is caused by a cloggedevaporator drain. Technician B says that this is causedby bacterial growth on the evaporator. Who is right?


36. When an A/C system is operating, a clicking orbuzzing noise is heard coming from the compressor.Technician A says that this noise means that the systemis overcharged. Technician B says that the noise couldbe due to air in the system. Who is right?


37. A customer complains that when parallel parking, hiscar repeatedly stalls, but only when the air conditioning ison. Technician A says that the power steering pressureswitch is defective. Technician B says that there is aproblem with the power steering pump. Who is right?


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38. All of the following are true statements aboutreceiver/driers EXCEPT:

A. They may have a sight glass located on the top.B. They store liquid refrigerant.C. They keep liquid refrigerant from entering

the compressor.D. They contain a desiccant to absorb moisture

from the system.

39. Technician A says that the pressure cycling switchis usually located on the accumulator. Technician Bsays that the refrigerant must be recovered from thesystem before the switch can be removed. Who is right?


40. Technician A says that the A/C system can becharged through the high or low side only when theengine is not running. Technician B says that the A/Csystem can be charged though the low side when theengine is running. Who is right?


41. An air conditioning check has uncovered a dis-charge in the system and compressor damage.Technician A says that after the repairs are made, tocheck the low-pressure cutoff switch. Technician B sayslubricating oil is carried by the refrigerant through thesystem. Who is right?


42. When checking recycled refrigerant for excess non-condensable gases (air), Technician A says that thecontainer must be stored at 65°F (18˚C) or above for 8hours out of direct sunlight, before checking the pres-sure. Technician B says if the pressure is higher thanthe limit shown for a given temperature, there is air inthe tank. Who is right?


43. The operation of the thermostatic switch depends onthe temperature of the:

A. condenserB. compressorC. evaporatorD. outside air

44. All of the following are causes for fan clutch replace-ment EXCEPT:

A. oil film on the back of the clutchB. no viscous dragC. fan speed does not increase as engine

warms upD. when engine is hot, fan stops spinning in

only two seconds after shut down

45. Technician A says that an ambient temperatureswitch protects the compressor from damage.Technician B says that an ambient temperature sensorprovides input for the Automatic Temperature Control(ATC) system. Who is right?


46. If a capillary tube were to break at some pointbetween its sensing bulb and the expansion valve, whataffect would it have on the valve?

A. The expansion valve would stick open.B. The expansion valve would stick closed.C. The expansion valve would stick in whatever

position it was in at the time of the break.D. There would be no affect on the expansion

valve.







47. A customer has a complaint of poor heat output.After checking the hoses running from the heater coreand finding them both to be hot, Technician A says theproblem could be a clogged heater core. Technician Bsays a misadjusted temperature control cable could bethe problem. Who is right?


48. The R134a retrofit label that is placed over the exist-ing R12 reference label must include all of the followinginformation EXCEPT:

A. name and address of the company or per-son that performed the retrofit

B. retrofit kit manufacturer’s nameC. date of the retrofitD. type and amount of refrigerant and lubricant

in the system

49. During the diagnosis of an ATC system, a troublecode is obtained that references the blend door feed-back sensor. Technician A says that the sensor shouldbe replaced. Technician B says that the sensor circuitshould be tested. Who is right?


50. A major cause for the depletion of the ozone layerhas been attributed to:

A. carbon monoxide (CO) fumes from automo-tive exhaust

B. unburned hydrocarbon (HC) emissions fromautomobile exhaust

C. the release of chlorofluorocarbons (CFCs)into the atmosphere

D. all of the above

51. Which of the following sensors is NOT an NTC ther-mistor?

A. in-vehicle sensorB. ambient sensorC. sunload sensorD. engine coolant temperature sensor

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80

The next two questions refer to the aboveschematic.

52. The cooling fan works on low speed but not on highspeed. Which of the following could be the cause?

A. a faulty fan control resistorB. an open in circuit 95S between the 95/95S

splice and the high speed relayC. a short to ground in circuit 95S between the

95/95S splice and the high speed relayD. a blown 60 amp fuse

53. This time the cooling fan works on high speed butnot on low speed. All of the following are possiblecauses EXCEPT:

A. a poor connection at the junction of circuit13S and the power distribution box

B. an open in circuit 30SC. a faulty fan control resistorD. an open in circuit 15 between the 15/15S

splice and the fan motor.







(Courtesy: Ford Motor Co.)

54. A customer with an SATC equipped vehicle com-plains that the car does not get cool enough on hotdays. Technician A says that the blend door actuator isprobably malfunctioning. Technician B says that the pro-grammer is the problem. Who is right?


55. A compressor clutch will not engage. All of the fol-lowing could be the cause EXCEPT:

A. a closed high-pressure cutout switchB. low refrigerant levelC. an open ambient temperature switchD. faulty compressor clutch coil

56. The inside of an EATC equipped vehicle never feelsas cool as the temperature setting. The A/C systemchecks out OK, including the sensors. Technician Asays there could be an obstruction in the aspirator tube.Technician B says the aspirator tube could be discon-nected from the duct. Who is right?


57. The ambient temperature sensor in an EATC sys-tem is being tested. Technician A says that the resis-tance of the sensor should increase as it is heated.Technician B says that, as the sensor resistancechanges, the computer reads the change in voltagedrop across the sensor. Who is right?


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82

The following three questions refer to the aboveschematic.

58. The blower motor works on all speeds except low.Technician A says that this could be caused by an openin the 1.8-ohm resistor. Technician B says that this

could be caused by an open in circuit 14S between theP/BL and P/O splice and the motor. Who is right?


(Courtesy: Ford Motor Co.)

59. The blower motor only works on high. Which of thefollowing could be the cause?

A. an open thermal limiterB. a blown 30 amp fuseC. an open in circuit 31D. an open in the P/BK wire between the P/BL

and P/BK splice and the blower switch

60. When the A/C damper door switch is placed in theMAX A/C position, the compressor clutch does notengage. However, a test light illuminates when placedat pin 1 of the A/C damper door switch. Which of the fol-lowing could be the cause?

A. an open in the P/BL wire of circuit 14SB. a faulty A/C damper door switchC. a blown 30 amp fuseD. a faulty A/C heater blower relay

61. At what percentage is refrigerant considered to bepure and safe for recovery?

A. 90%B. 95%C. 98%D. 100%

62. All of the following could cause lower than normalhigh-side pressure EXCEPT:

A. missing air damB. low refrigerant chargeC. worn compressorD. restricted orifice tube

63. Two Technicians are discussing an A/C systemretrofit. Technician A says that a high-pressure cutoutswitch must be added to the system. Technician Bsays that the receiver/drier should be replaced. Who isright?


64. A customer complains about a hissing noise com-ing from under the hood after turning off the car. ATechnician says the noise is coming from the A/C sys-tem and is:

A. a normal conditionB. system pressures equalizingC. a refrigerant leakD. both A and B

65. A customer complains of low air flow through theinstrument panel duct outlets. Which of the followingcould be the cause?

A. faulty blower motorB. clogged passenger compartment air filterC. stuck mode doorD. all of the above

66. All of the following are classifications of antifreezeEXCEPT:

A. Inorganic Additive Technology (IAT)B. Organic Additive Technology (OAT)C. Hybrid Inorganic Additive Technology (HIAT)D. Hybrid Organic Additive Technology (HOAT)

67. Vehicles with Dual Zone climate control have aseparate __________ for the passenger side of thevehicle.

A. mode doorB. blend doorC. heater coreD. evaporator core

68. When using an electronic refrigerant leak detector,all of the following should be observed EXCEPT:

A. Leak detectors are very sensitive to manytypes of gases. If the area is contaminatedwith refrigerant or other gases, use a fan orcompressed air to blow the excess refriger-ant away.

B. Pass the probe around the top of compo-nents and hoses as refrigerant is lighterthan air and tends to rise.

C. Don’t move the probe faster than one inchper second.

D. Never allow the probe to contact any sur-face, to prevent contamination of the sens-ing tip.

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69. Technician A says that mineral deposits canrestrict air flow through the radiator. Technician B saysthat internal restrictions in the radiator can be detectedfrom the outside. Who is right?


70. A typical refrigerant identifier can detect all of thefollowing EXCEPT:

A. R134aB. HydrocarbonsC. AirD. R744


NOTES

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Answers to Study-Guide Test Questions

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1. The correct answer is A. Evacuating an A/C sys-tem removes air and moisture from the system. Thereceiver/drier may contain a filter or strainer to catchand trap foreign particles and dirt, but this remains inthe receiver/drier and is not removed during the evacu-ation procedure.

2. The correct answer is B. The compressor clutchbearing allows the rotor/pulley assembly to spin inde-pendently of the compressor shaft when the A/C sys-tem is off. When the engine is running and the A/Csystem is off, the compressor clutch bearing is spin-ning. When the A/C system is turned on, the rotor/pul-ley assembly and the armature are locked together bythe magnetic action of the compressor clutch coil.

3. The correct answer is B. Low pressure on both thelow side and the high side indicates a low refrigerantcharge.

4. The correct answer is D. According to the Clean AirAct, recovery/recycling equipment must have shutoffvalves located within 12-in. (30 cm) of the hoses’ ser-vice ends so that refrigerant discharge to the atmo-sphere can be kept to a minimum.

5. The correct answer is B. The technician should waitfive minutes and watch the gauges to see if there isany residual pressure. If there is, repeat the process toremove any remaining refrigerant until the A/C systemholds a stable vacuum for at least five minutes.

6. The correct answer is D. A low pressure reading onthe low side and a heavy frost accumulation on theinlet side of the TXV indicates a clogged screen at theexpansion valve inlet or a TXV stuck closed.

7. The correct answer is B. Answer D is incorrectbecause if the blower fuse was blown or circuit breakertripped, the blower would not work at all. Answer A isincorrect because a blower relay is generally only usedfor the high blower speed and this is working. AnswerC, the blower switch is a possible cause but the mostlikely cause for operation on only high speed is that aportion of the resistor assembly is burned out.

8. The correct answer is C, both technicians are right.If, during hard acceleration, air routing changes byitself, it’s probably due to a leak in the system or afaulty check valve in the vacuum reservoir. A com-plaint that the mode shifts from the dash to the floor atwide-open throttle is evidence that the system isn’tholding vacuum.

9. The correct answer is A. If the engine is startedwhile pressure testing a cooling system and the pres-sure immediately increases, there could be a headgasket leak, but not into the crankcase. The coolantmay be going out the tailpipe, but since this is a latemodel gasoline engine vehicle and equipped with acatalytic converter, there is no white smoke from theexhaust because the converter super-heats thecoolant into such a fine vapor that it is not noticeable.

10. The correct answer is A. Systems using an expan-sion valve have a receiver/drier between the valve andcondenser, while orifice tube systems have an accu-mulator between the evaporator and compressor.Technician B is wrong because on R134a systems,the low-side service port is the smaller one.

11. The correct answer is B. If the system reacts witha change to one or two inputs but not to the third, theproblem is most likely confined to the single sensor orits circuit. But if no reaction is observed on any of theunits, or only a partial reaction is seen, the problem isusually with the programmer.

12. The correct answer is C. When removing the ori-fice tube with an extractor tool, do not twist or rotatethe orifice tube in the line as it can break. If an orificetube breaks during removal, special tools are availableto extract broken orifice tubes. All of the other answersare methods of orifice tube replacement.

13. The correct answer is D. When charging aretrofitted system with R134a refrigerant, the systemwill only require 80-90 percent of the original R12charge amount.

14. The correct answer is B. Technician A is wrongbecause propane gas leak detectors cannot detectR134a. Technician B is right, but he must make surethe electronic leak detector is designed for R134a, asmany older units are not.

15. The correct answer is C. Desiccants are not uni-versal and different types must be used with differentrefrigerants and lubricating oils. When a system isretrofitted, the replacement receiver/drier or accumula-tor has XH-7 or XH-9 desiccant.

16. The correct answer is B. Technician A is wrongbecause if the clutch coil was defective, the compres-sor clutch would not engage. Technician B is correctbecause, since the compressor clutch engages when12 volts is directly applied, the problem is in the com-pressor control circuit, which includes the pressurecycling switch.

17. The correct answer is A. Fogged windows thatsmear when wiped and moisture on the passengerfloor are telltale signs of a leaking heater core.Technician B is incorrect because, while a cloggedevaporator case drain could cause the case to fill upwith moisture and spill out onto the floor, it would notcause a slimy film on the windows.

18. The correct answer is C, both technicians areright. Knocking noises from the compressor usuallyindicate internal damage, especially on piston-typecompressors. However, always check the compressormounting and brackets before condemning the com-pressor for noise. A loose mounting can cause knock-ing noises from the compressor area that may bemistaken for internal compressor noise.

19. The correct answer is D. A stuck open heater con-trol valve could cause problems when heat is notwanted, but because coolant flow to the heater core isnot interrupted, the heater valve would not cause poorheater performance. A defective temperature blenddoor actuator could cause poor heat if the blend doorwas stuck in the wrong position. Radiator coolant tem-perature below 150˚F (66˚C) would indicate a missingor stuck open thermostat, which could also cause poorheater performance. A heater core return hose that ismuch cooler than the inlet hose means that the heatercore is plugged or air bound, also causing poor heat.

20. The correct answer is D. Although the air tempera-ture at the center outlet would be about the same, ifthe condenser is plugged, the manifold gauge read-ings would be high. All of the other answers are possi-ble causes for the symptoms in the question.

21. The correct answer is B. There must be at least 50psi of refrigerant pressure in the system in order for aleak detector to be able to sense a leak. Refrigerantmay have to be added to the system to achieve this.

22. The correct answer is A. During a retrofit, the newR134a service fittings are usually conversion fittingsthat are installed on the existing R12 fitt ings.Technician B is wrong because if the R12 fittings arenot converted, they must be permanently capped.

23. The correct answer is B. Most temperature sen-sors can be tested for resistance and voltage drop. Ingeneral, the sensor should be replaced if its resistanceis not within specification. Since a temperature sen-sor’s resistance varies with temperature, check thesensor voltage against temperature and compare tomanufacturer’s specifications.

24. The correct answer is C, both technicians areright. Technician A is correct because the high-pres-sure cutout switch should break the circuit to the com-pressor clutch if it detects pressures above a presetlevel. If the compressor continues to run when pres-sure passes the threshold of the switch calibration, theswitch is defective. Technician B is also right becausean obstruction to air flow through the condenser cancause excessive high-side pressure.

25. The correct answer is C, both technicians are right.During operation, the clutch may cycle on and off severaltimes each minute. Insufficient refrigerant causes rapidchange in heat load on the evaporator, which affectssystem pressures. If the clutch cycles rapidly, it may be asign of low refrigerant charge. A defective thermostaticswitch may not be engaging the compressor clutch longenough. The thermostatic switch has a capillary tubeattached to the evaporator outlet or inserted between theevaporator core fins to sense the temperature. This cap-illary is attached to a switch that opens and closes, asnecessary, to cycle the compressor.

26. The correct answer is D. To properly evacuate anA/C system, the vacuum pump should be operated fora minimum of 30 minutes.

27. The correct answer is B. Technician A is wrongbecause a special tool is only required to disconnectspring lock fittings.

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28. The correct answer is D. There are filters that fitinto both the high and low sides of the system. All ofthe other statements ate true concerning in-line filters.

29. The correct answer is C, both technicians areright. If there is foam, the charge is low, but if thereare only a couple of bubbles, it is probably OK. A fewbubbles when the compressor cycles on is normal. Oilstreaks in the sight glass usually indicate a low chargeand that the compressor is pumping oil from its sump.

30. The correct answer is C, both technicians areright. Moisture in the A/C system can ice up in theexpansion valve and block refrigerant flow. On sys-tems with R12, moisture can combine with the chlorinein the R12 to form hydrochloric acid. These chemicalscan corrode metals and attack rubber parts.

31. The correct answer is D. A disengaged clutch typeradiator fan would not cause low heater output. All ofthe other answers are possible causes of low heateroutput.

32. The correct answer is D. A broken compressorreed valve could not cause the high-side pressure tobe above specifications.

33. The correct answer is B. To prevent overfilling dur-ing transfer of refrigerant, never fill a container to morethan 60 percent of its gross weight rating.

34. The correct answer is B. Regardless of what con-dition the door is in, the key here is that the gaugereading is zero, meaning there is a vacuum leak in theactuator.

35. The correct answer is C, both technicians areright. If the drain at the bottom of the evaporator casebecomes clogged and water collects and stagnates, orif the surface of the evaporator remains too moist dueto high humidity, bacteria can grow in the stagnantwater or on the evaporator surface and cause an odor.This odor is then sent into the passenger compartmentby the blower motor.

36. The correct answer is C, both technicians areright. A clicking or buzzing noise coming from the com-pressor is a sign that the system is overcharged andliquid refrigerant is entering the compressor. Unlesssome refrigerant is removed, severe compressor dam-age may result. This noise could also result from air inthe system.

37. The correct answer is A. The power steering pres-sure switch is installed in the power steering systemand reports on high pressure conditions caused by aload being placed on the engine by the power steeringpump. The computer may decide to temporarily shutdown the compressor to prevent engine stalling or lowidle speed, or it could also raise idle speed throughcontrol of an idle speed control device. During parallelparking maneuvers, the steering wheel is most likelybeing moved to full lock at some point, increasing pres-sure. Technician A is right because, if this increasedpressure is not being communicated to the computerby the switch, the A/C compressor will continue to runwith its load on the engine or the idle speed will not beraised enough to keep the engine from stalling.Technician B is wrong because if the problem was withthe power steering pump, the stalling would occurregardless of whether the A/C was on.

38. The correct answer is C. The receiver/drier islocated in the high side of the system, between thecondenser and evaporator, ahead of the expansionvalve. It stores liquid refrigerant until needed by theevaporator. The accumulator is the component thatkeeps liquid refrigerant from entering the compressor,but accumulators are used in systems with orificetubes, not expansion valves.

39. The correct answer is A. The pressure cyclingswitch senses the low-side pressure near the evapora-tor outlet and is usually found on the accumulator.Technician B is wrong because the switch is oftenmounted in a Schrader fitting so it can be replacedwithout the loss of refrigerant.

40. The correct answer is C, both technicians areright. Charging the system can be performed througheither the high side or low side when the engine is notrunning, but must be done only through the low sidewhen the engine is running. This safety measure pre-vents high-side pressure from entering the refrigerantcontainer and possibly causing an explosion.


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41. The correct answer is C, both technicians areright. The purpose of the low-pressure cutoff switch iscompressor protection. The compressor clutch circuitis opened if the pressure in the system drops too low.This would be an indication that the system has lostsome or all of its refrigerant charge. Since the lubricat-ing oil is carried by the refrigerant, a loss could causedamage to the compressor if it were allowed to oper-ate without sufficient lubrication.

42. The correct answer is B. To purge the air, connectthe tank to the recovery/recycling machine and slowlyvent the air vapor from the top of the container.Continue venting until the pressure falls below the limitshown on your chart. If the pressure inside the con-tainer still exceeds the pressure limit shown, recyclethe entire contents. Technician B is wrong because thecontainer must be stored for 12 hours, not eight.

43. The correct answer is C. The thermostatic switch,which is used to cycle the A/C compressor on and off,depends on the temperature of the evaporator in orderto operate.

44. The correct answer is D. A properly operatingclutch should stop the fan from spinning within twoseconds after a hot engine shut down. All of the otheranswers are indications of a defective fan clutch.

45. The correct answer is C, both technicians areright. In non-ATC systems, the function of the ambienttemperature switch is to inhibit compressor clutchoperation in cold ambient temperatures. This functionmainly protects the compressor from poor or no lubri-cation, which could be the result of cold refrigerant oil.In ATC systems, the ambient temperature sensorsenses ambient outside temperature. As ambient orinterior temperatures stray, the sensors pick up thechange and the system adjusts the outlet duct temper-ature accordingly to compensate for the temperaturechanges.

46. The correct answer is B. Expansion valves areusually spring loaded devices with a diaphragm that islinked to a plunger. Without any pressure against thediaphragm from the gas in the capillary tube, thespring inside the expansion valve would cause thevalve to stick closed.

47. The correct answer is B. If both hoses leading tothe heater core are hot, coolant is circulating throughthe heater core. One hose that is significantly coolerthan the other would indicate a clogged heater core.However, if the temperature control cable is incorrectlyadjusted, the temperature blend door may not allowenough warm air to enter the passenger compartmentfor sufficient heating.

48. The correct answer is B. The parts used during aretrofit don’t necessarily have to come from a kit andeven if they do, that information is not required on theretrofit label. All of the other information is required tobe listed.

49. The correct answer is B. Fault codes usually onlyindicate which circuit the problem is in; they don’t nec-essarily indicate which component in the circuit hasfailed. The problem could be caused by a loose con-nection, improper modification, or a broken wire, soperform a thorough inspection when diagnosing a mal-function. Ensure that all grounds are clean and makinggood contact. If basic mechanical and electricalchecks fail to locate the problem, follow manufacturer’selectronic system test procedures.

50. The correct answer is C. The release of CFCs intothe atmosphere has been found to be a major cause ofozone layer depletion.

51. The correct answer is C. The sunload sensor is aphotovoltaic diode. All of the other sensors listed areNTC thermistors.

52. The correct answer is B. Answer A is wrongbecause the fan control resistor does not affect high-speed fan operation. Answer C is wrong because ashort to ground here will blow the 20-amp fuse andneither fan will work. Answer D is wrong because if the60-amp fuse is blown, neither fan will work.

53. The correct answer is D. If there is an open in cir-cuit 15 between the 15/15S splice and the fan motor,the motor will not run at all. All of the other answersare possible causes for no low speed blower motoroperation.

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54. The correct answer is D, neither technician isright. Both technicians are jumping to conclusions. Toa find the problem, a logical diagnostic procedure mustbe followed or parts may be replaced unnecessarily.This includes performing a preliminary inspection ofthe A/C system and checking refrigerant pressuresbefore condemning any part of the ATC system.

55. The correct answer is A. The high-pressure cutoutswitch is normally closed. It opens the compressorclutch circuit when high-side pressures are excessivein order to protect the compressor. All of the otheranswers would cause the compressor clutch not toengage.

56. The correct answer is C, both technicians areright. The in-vehicle temperature sensor is located inthe aspirator, which is located in the dashboard. Theaspirator tube is connected to a heater-A/C duct. Theair flowing in the duct past the tube creates a vacuum,drawing in-vehicle air past the sensor. If there is anobstruction in the aspirator tube or the tube is discon-nected from the duct, air will not be drawn past the in-vehicle temperature sensor and the sensor will not beable to accurately measure the temperature inside thevehicle. This could account for the discrepancybetween the temperature setting and the actual tem-perature inside the vehicle.

57. The correct answer is B. The ambient temperaturesensor is an NTC (Negative Temperature Coefficient)thermistor. When an NTC thermistor is heated, theresistance should drop, and when it is cooled, resis-tance should increase.

58. The correct answer is A. Technician B is wrongbecause if there is an open between the P/BL and P/Osplice and the motor, the motor will not run at all.

59. The correct answer is A. An open thermal limiterwould prevent the blower motor from working on anyspeed but high. The other answers are incorrectbecause any of these causes would prevent theblower motor from working at all.

60. The correct answer is B. A faulty A/C damper doorswitch or a problem in the circuit between the switchand the A/C clutch cycling switch could be the prob-lem. Since the test light showed that there is powergoing to the A/C damper door switch, all of the othercomponents listed are OK.

61. The correct answer is C. Refrigerant is consideredpure and safe for recovery if it is at least 98% byweight of a single type of refrigerant. If the refrigerantin the system is less than 98% pure, it should be con-sidered contaminated and reclaimed or destroyed.

62. The correct answer is A. A lower than normalrefrigerant charge and excessive internal wear wouldboth cause the compressor to develop less dischargepressure. A restricted orifice tube would cause refriger-ant flow through the system to be slowed. When therefrigerant spends more time in the evaporator, itstemperature and pressure are slightly reduced. Amissing air dam would cause an air flow problemthrough the condenser and the radiator. The reducedair flow and possible engine overheating would bothcause higher than normal high side pressure.

63. The correct answer is C, both Technicians areright. If it does not have one, a high-pressure cutoutswitch must be added to the system to stop compres-sor operation before high-side pressure reaches thepoint of opening the high-pressure relief valve andreleasing refrigerant into the atmosphere. Thereceiver/drier should be replaced because all refriger-ants do not use the same type of desiccant. R134asystems use XH-7 or XH-9 desiccant.

64. The correct answer is D. The hissing noise is nor-mal and caused by high-side pressure going throughthe refrigerant metering device as system pressuresequalize.

65. The correct answer is D. A blower motor that doesnot run on high speed or higher speeds due to adefective relay or resistor would cause reduced airflow. A clogged passenger compartment air filter wouldcreate an obstruction and also reduce air flow. Finally,a mode door stuck between two positions would createthe impression of reduced air flow because the avail-able air would be routed to two places (i.e., the floorand the dash) instead of one.

66. The correct answer is C. Inorganic AdditiveTechnology (IAT) antifreeze uses inorganic phos-phates and silicates to provide corrosion protection.Organic Additive Technology (OAT) antifreeze usesorganic acids to protect then iron and aluminum in thecooling system. Hybrid Organic Additive Technology(HOAT) antifreeze uses both silicate and organic acidcorrosion inhibitors for extended service life.

67. The correct answer is B. Vehicles with Dual Zoneclimate control have a separate blend door for the pas-senger side. The passenger can adjust a separatetemperature control, which in turn controls the blenddoor and the amount of air flowing through the heatercore for the passenger side of the vehicle.

68. The correct answer is B. Make sure that you passthe probe around the bottom of components andhoses as refrigerant is heavier than air and tends tosettle.

69. The correct answer is B. Technician A is wrongbecause mineral deposits can restrict coolant flowinside the radiator, not air flow through the radiator.Look inside the radiator for large amounts of mineraldeposits at the ends of the core tubes. Technician B isright because an infrared surface thermometer can beused to scan the surface of the radiator. With theengine hot and idling, the radiator should be warmestnear the inlet and gradually cool toward the outlet. Ifthere are areas that are considerably cooler than theinlet, then there may be restrictions at those areas.

70. The correct answer is D. Systems that use R744refrigerant, which is pure CO2, are still under develop-ment. Typical refrigerant identifiers that are currentlyavailable can detect R12, R134a, R22, air and hydro-carbons.

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NOTES

----aa----

aaccccuummuullaattoorr -- a component used to store or holdliquid refrigerant in an air conditioning system thatalso contains a desiccant.

actuator - a control device that delivers mechanicalaction in response to a vacuum or electrical signal.

air conditioning (A/C) - a system that cools anddehumidifies the air entering the passengercompartment of a vehicle.

air ducts - tubes, channels or other tubular structuresused to carry air to a specific location.

air gap - the space or gap between the compressordrive hub and pulley assembly.

ambient temperature - the temperature of the airsurrounding an object.

ambient temperature switch - a switch thatprevents air conditioner operation below a certainambient temperature.

amplifier - a circuit or device used to increase thevoltage or current of a signal.

antifreeze - a material such as ethylene glycol whichis added to water to lower its freezing point; used in anautomobile’s cooling system.

atmospheric pressure - the weight of the air at sealevel (14.7 lbs. per sq. in.) or at higher altitudes.

automatic temperature control (ATC) system -a climate control system that uses the heating and airconditioning systems to maintain the interiortemperature selected by the vehicle’s passengers.

axial - having the same direction or being parallel tothe axis or rotation.

--b--

blend door - a door in the heating and airconditioning system that controls the temperature ofthe air going into the passenger compartment.

blower motor - the electric motor, which drives thefan that circulates air inside the vehicle passengercompartment.

boiling point - the temperature at which a liquidturns to vapor.

British Thermal Unit (BTU) - a unit ofmeasurement; the amount of heat that is required toraise the temperature of one pound of water by onedegree F.

--c--

capillary tube - a thin, gas-filled tube that sensesthe temperature of the evaporator and relays thisinformation to the thermostat and/or expansion valve.

Celsius - the basis of the metric system oftemperature measurement in which water’s boilingpoint is 100ºC and its freezing point is 0ºC.

charge - to fill, or bring up to the specific level, an A/Csystem with refrigerant; the required amount ofrefrigerant for an A/C system.

chlorofluorocarbon (CFC) - any organic chemicalcompounds made up of carbon, chlorine and fluorineatoms, usually used in refrigeration. R12 is a CFC.

clutch cycling switch - a device that opens andcloses the circuit that engages the air conditioningcompressor clutch based on pressure or temperature.

compressor - an engine driven device thatcompresses refrigerant gas and pumps it through theair conditioning system.

condensation - the process of a vapor becoming aliquid; the opposite of evaporation

condense - to cool a vapor to below its boiling point,where it then condenses into a liquid

condenser - a device, similar to a radiator, in whichthe refrigerant loses heat and changes state from ahigh-pressure gas to a high-pressure liquid as itdissipates heat to the surrounding air.

coolant - a mixture of water and ethylene glycolbased antifreeze that circulates through the engine tohelp maintain proper temperatures

cooling fan - a mechanically or electrically drivenpropeller that draws air through the radiator.

Glossary of Terms

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Glossary of Terms

94

cooling system - the system used to remove excessheat from an engine and transfer it to the atmosphere.Includes the radiator, cooling fan, hoses, water pump,thermostat and engine coolant passages.

core - in automotive terminology, the main part of aheat exchanger, such as a radiator, evaporator orheater. Usually made of tubes, surrounded by coolingfins, used to transfer heat from the coolant to the air.

corrosion - the eating into or wearing away of asubstance gradually by rusting or chemical action.

crossflow radiator - a radiator in which coolantenters on one side, travels through tubes, and collectson the opposite side (see downflow radiator).

cycling clutch system - an A/C system that controlstemperature by switching the compressor clutch on-and-off.

--d--

deflection - a turning aside, bending or deviation;bending or movement away from the normal positiondue to loading.

degree - used to designate temperature readings or 1degree as a 1/360 part of a circle.

dehumidify - to remove moisture (humidity) from theair.

desiccant - any hygroscopic material that removesand traps moisture, usually found in a bag in theaccumulator or receiver/drier in air conditioningsystems.

diagnostic trouble code (DTC) - a code thatrepresents and can be used to identify a malfunction ina computer control system.

diaphragm - a flexible, impermeable membrane onwhich pressure acts to produce mechanicalmovement.

diode - a simple semiconductor device that permitsflow of electricity in one direction but not the other.

discharge - to remove the refrigerant from an airconditioning system.

displacement - the volume the cylinder holdsbetween the top dead center and bottom dead centerpositions of the piston.

downflow radiator - a radiator in which coolantenters the top of the radiator and is drawn downwardby gravity (see crossflow radiator).

--e--

electromagnet - a magnet formed by electrical flowthrough a conductor.

electromagnetic induction - moving a wire througha magnetic field to create current flow in the wire.

electromechanical - refers to a device thatincorporates both electrical and mechanical principlestogether in its operation.

electronic - pertaining to the control of systems ordevices by the use of small electrical signals andvarious semiconductor devices and circuits.

electronic control module (ECM) - the computerin an electronic control system, also known as anelectronic control unit (ECU).

engine coolant temperature (ECT) sensor - asensor, which works by a negative coefficientthermistor, that loses resistance as its temperaturegoes up (just like the intake air temperature sensor).When the computer applies its 5-volt reference signalto the sensor, this voltage is reduced through a groundcircuit by an amount corresponding to the temperatureof the engine coolant.

evacuate - the process of applying vacuum to aclosed refrigeration system to remove air andmoisture.

evaporation - the process through which a liquid isturned into vapor.

evaporator - a heat exchanger, in which low-pressure refrigerant flows and changes state,absorbing heat from the surrounding air.

--f--

Fahrenheit - a scale of temperature measurementwith the boiling point of water at 212˚F. In the metricsystem, water’s boiling point is 100˚Celsius.

fan - a mechanically or electrically driven propellerthat draws or pushes air through the radiator,condenser, heater core or evaporator core.

fan clutch - a device attached to a mechanicallydriven cooling fan that allows the fan to freewheelwhen the engine is cold or the vehicle is driven atspeed.

fan shroud - an enclosure that routes air through theradiator cooling fins.

Freon - Dupont registered trade name for R12refrigerant (dichlorodifluoromethane).

--g--

gauge set - the set of gauges that attaches to thehigh and low side of the A/C system and used fordiagnosis. Also called a manifold gauge set.

ground - the negatively charged side of a circuit. Aground can be a wire, the negative side of the batteryor the vehicle chassis.

--h--

head pressure - the pressure of the refrigerant at thecompressor outlet.

heater core - a radiator-like device used to heat theinside of a vehicle. Hot coolant is pumped through it bythe water pump, and heat from the coolant moves fromthe heater core to the passenger compartment as theblower fan forces air through it.

high side - the high-pressure half of an A/C system,usually refers to all components between thecompressor outlet and the expansion valve or orificetube.

--l--

latent heat of condensation - the amount of heatgiven off as a vapor changes state from a gas to aliquid without the temperature changing.

latent heat of evaporation - the amount of heatneeded for a liquid to change state to a vapor withoutthe temperature changing.

leak detector - a tool used to locate refrigerant leaks.

liquid line - the tube and/or hose leading from theoutlet of the condenser to the expansion valve ororifice tube.

low side - the suction side of an A/C system betweenthe evaporator core inlet (after the expansion valve ororifice tube) and the compressor.

lubrication - reducing friction between moving parts.

--m--

magnet - any body with the property of attracting ironor steel.

magnetic field - the areas surrounding the poles ofa magnet, which are affected by its forces of attractionor repulsion.

microprocessor - the portion of a microcomputer thatreceives sensor input and handles all calculations.

multimeter - a tool that combines the functions of avoltmeter, ohmmeter and ammeter together in onediagnostic instrument.

--n--

negative temperature coefficient thermistor - athermistor that loses electrical resistance as it getswarmer. The temperature sensors for the computercontrol system are negative temperature coefficientthermistors. The effect is to systematically lower the 5-volt reference voltage sent them by the computer,yielding a signal that corresponds to the temperatureof the measured source. Typically the ECT and IATsensors use this principle.

--o--

ohm - a unit of measured electrical resistance.

open circuit - electrical circuit that has an intentional(switch) or unintentional (bad connection) break in thewire.

orifice - a precisely sized hole that controls the flowof fluid.

orifice tube - used in some air conditioning systems,a component with a fixed opening through whichrefrigerant passes as it is metered into the evaporatorcore.

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--p--

polyalkyline glycol (PAG) oil - lubricant used withA/C systems containing R-134a refrigerant.

pressure - the exertion of force upon a body.Pressure is developed within the cooling or A/Csystem and is measured in pounds per square inch ona gauge.

psi - measurement of pressure in pounds per squareinch.

--r--

R12 - the generic term for CFC refrigerant used inolder A/C systems. Also called Freon.

R134a - generic term for a modern refrigerant thatdoes not contain CFCs and does not harm the ozonelayer.

radiator - the part of the cooling system that acts asa heat exchanger, transferring heat to atmosphere. Itconsists of a core and holding tanks connected to thecooling system by hoses.

radiator cap - a device that seals the radiator andmaintains a set pressure in the cooling system.

receiver/drier - an A/C system component intowhich high-pressure liquid refrigerant flows and istemporarily stored and dehydrated, usually locatedbetween the condenser outlet and expansion valve.

reclaim - to send refrigerant to an off-site facilitywhere it is restored to its original purity so that it maybe reused.

reciprocating - an up-and-down or back-and-forthmotion.

recover - to remove refrigerant from a system andstore it temporarily.

recycle - to remove contaminants such as moisture,particulates, etc. from refrigerant and re-introduce itinto the A/C system.

refrigerant - a chemical compound used in an A/Csystem to remove heat from the evaporator andtransfer it to the condenser.

refrigerant cycle - the complete loop or circuit thatrefrigerant passes through as it changes state from avapor, to a liquid, then back to a vapor.

refrigerant oil - either a mineral or synthetic oildesigned specifically for A/C systems.

relay - an electromagnetic switch that uses lowamperage current to control a circuit with highamperage.

residual pressure - remaining or leftover pressure.

residue - surplus; what remains after a separation.

resistance - the opposition offered by a substance orbody to the passage of electric current through it.

retrofit - to convert an older A/C system that usedR12 to use R134a refrigerant, usually by replacingvarious components.

rotary - refers to a circular motion.

--s--

Schrader valve - a spring operated valve used toopen and close the service outlets in an A/C system.They are the service valves used to attach manifoldgauges and to charge or evacuate the system.

serpentine belt - multiple ribbed belts that wraparound and drive various engine mountedcomponents.

service port - any of the various designs of fittingsthat allow service tools such as manifold gauges to beattached to an A/C system. See also Schradervalve.

servo - a device, such as an electric motor orhydraulic piston that is controlled by an amplifiedsignal from a low power command device.

sight glass - a window in the high-pressure side ofthe A/C system, usually in the receiver/drier, toobserve the refrigerant for signs of bubbles and/ormoisture.

slip - condition caused when a driving part rotatesfaster than a driven part.

suction - suction exists in a vessel when the pressureis lower than the atmospheric pressure.

Glossary of Terms

96

suction line - the low-side tube and/or hose leadingfrom the evaporator core outlet to the compressorinlet.

superheat - the addition of more heat to a gas after ithas already vaporized; the heat added to vaporizedrefrigerant after it has changed state from a liquid to agas.

superheat switch - a switch, usually mounted on thecompressor on certain A/C systems, which completesthe circuit to the thermal limiter switch.

--t--

technical service bulletin (TSB) - informationpublished by vehicle manufacturers that describeupdated service procedures that should be used tohandle vehicle defects.

tension - effort that elongates or stretches material.

thermal limiter - a component, similar to a fuse,which blows to open the compressor clutch circuitwhen the superheat switch detects low A/C systempressure.

thermistor - a temperature sensitive variable resistorin which the resistance decreases as its temperatureincreases.

thermostat - a device installed in the cooling systemthat allows the engine to come to operatingtemperature quickly and then maintains a minimumoperating temperature.

thermostatic expansion valve (TXV) - used onsome air conditioning systems, a temperaturesensitive device that meters the flow of refrigerant intothe evaporator core. Also called an expansion valve.

--v--

vapor - a substance in a gaseous state. Liquidbecomes vapor when brought above the boiling point.

volt - a unit of measurement of electromotive force.One volt of electromotive force applied steadily to aconductor of one-ohm resistance produces a current ofone ampere.

voltage drop - voltage lost by the passage ofelectrical current through resistance.

voltmeter - a tool used to measure the voltageavailable at any point in an electrical system.

--w--

water pump - device used to circulate coolantthrough the engine.

water valve - a device used to control the flow of hotcoolant to the heater core, operated by cable, vacuumor electrically.

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