Air conditioning 9-12

During heavy acceleration a vehicle has sluggish performance when the air conditioning is on. Which of the following is the most likely cause?

A faulty engine load sensor cut-off system.

In the case and duct system the air distribution mode doors may be operated by all of the following Except: a. Potentiometers b. Electrically powered motors c. Cable d. Vacuum motors

Potentiometers

Under the CAA, anyone performing repairs to a motor vehicle air conditioning system for pay must

be certified, and use recovery/recycle equipment

Technician A says a compressor clutch may be cycled based on refrigerant (evaporator) temperature. Technician B says the compressor clutch may be cycled based on refrigerant pressure. Who is correct?

both

Technician A says changing any part of an original design changes the performance of the equipment. Technician B says if an extra fan and motor are added, a relay should also be added. Who is correct?

both

Technician A says low pressure exists in an operating air conditioning system from the metering device outlet to the compressor inlet. Technician B says that high pressure exists in an operating air conditioning system from the compressor outlet to the metering device inlet. Who is correct?

both

Technician A says mode doors may be electrically operated. Technician B says mode doors may be vacuum operated. Who is correct?

both

Technician A says a check valve allows flow in one direction only. Technician B says a check valve blocks flow in one direction only. Who is correct?

both

Technician A says to always recover the refrigerant before removing a pressure switch. Technician B says a different pressure range switch may be installed to compensate for a worn but serviceable compressor. Who is correct?

. Neither A nor B

An average rating of an air conditioning system fuse or circuit breaker is ____ amperes. 30 to 100 10 to 20 15 to 25 20 to 30

20-30

Technician A says after the retrofit is complete, a function test should be made. Technician B says system pressures and temperatures for HFC-134a should be the same as for CFC-12. Who is correct?

A

Evacuation of an air conditioning system is being discussed. Technician A says one factor affecting the speed of evacuation is internal restrictions. Technician B says all of the oil is usually removed during evacuation. Who is correct?

A only

In the MIX/BILEVEL position, conditioned air is delivered to the ____ outlet on some vehicles.

floor and defrost

Retrofits are being discussed. Technician A says the procedure involves replacing the refrigerant. Technician B says new service fittings must be installed. Who is correct?

A CHECK THIS ONE

The temperature fluctuates between hot and cold on a vehicle equipped with an automatic temperature control system. Which of the following is the most likely cause?

A disconnected in-car temperature sensor aspirator tube.

The following statements regarding the relationships between the cooling system and air-conditioning system are all true, EXCEPT: ​

Ambient air first passes through the radiator, then the condenser.

Technician A says debris in the fresh air intake can contaminate the refrigerant. Technician B says cleaning the fresh air inlet should be part of a periodic preventative maintenance schedule. Who is correct?

B

Technician A says the greatest problem in servicing the case and ducts is lack of specialty tools needed. Technician B says the greatest problem in servicing the case and ducts is lack of service information needed. Who is correct?

B

=Technician A says most compressor clutches are driven from the engine crankshaft by a belt. Technician B says late model hybrid electric vehicles use an integrated electric motor to drive the compressor. Who is correct?

BOTH

Technician A says one way to determine the condition of vacuum hoses is by visual inspection. Technician B says a vacuum leak can often be heard. Who is correct?

BOTH

A technician finds an air conditioning clutch will not engage. Upon initial testing the compressor is receiving both proper power and ground at the compressor clutch electrical connector, in addition the compressor input shaft turns freely by hand. Which of the following is the most likely cause?

COMPRESSOR CLUTCH AIR GAP TOO LARG

All of the following statements about thermostatic expansion vales on retrofitted systems are true, EXCEPT: a. If a defective expansion valve is replaced, always use a model designed for the system refrigerant. b. An R-134a valve used in a R-12 system will have reduced superheat. c. The expansion valve does not have to be replaced when retrofitting a system from R-12 to R-134a. d. A R-12 expansion valve used in an R-134a system will result in higher superheat and reduced evaporator efficiency.

D

When should the cabin air filter be replaced if the vehicle is operated in dusty or high pollution conditions?

Every 15,000 miles.

The concern in the world community has shifted from the threat of ozone-depleting chemicals to a concern over which of the following?

Global warming

All of the following air-conditioning system sensors are varying resistive sensors EXCEPT:​

Infrared Temperature Sensor

Which of the following is the best description of a pressure switch designated nc?

It is held closed during normal pressure conditions.

The air conditioning compressor will not engage. When a scan tool is connected it indicates that there is no A/C request signal. Technician A says that the refrigerant system may have a faulty thermostatic expansion valve. Technician B says that an engine cooling system thermostat which is opening too soon could be the cause. Who is correct?

Neither A nor B

The Clean Air Act of 1990 says after July 1, 1992, which of the following refrigerants may be intentionally vented?

None of the above

When the A/C switch is in the off position on a vehicle with a cycling clutch type system the compressor clutch stays engaged. Which of the following is the most likely cause?

The compressor clutch relay is stuck closed.

All of the following statements about a typical system set to MAX (maximum) cooling are true, EXCEPT: The compressor clutch is engaged. The outside/recirculate air door is opened to outside air. Airflow is from inside the car, through the evaporator, and out through the panel registers. The blower is running.

The outside/recirculate air door is opened to outside air.

On a vehicle equipped with an automatic temperature control system the blower motor will not function when the vehicle is first started and heat is selected. Which of the following is the most likely cause?

The system is functioning normally.

Which of the following desiccants should be used with HFC-134a refrigerant?

XH7 AND XH9

All of the following statements about variable displacement compressors are true, EXCEPT: Variable displacement compressors have a cycling clutch.. b. Variable displacement compressors do not have a cycling clutch. c. Variable displacement compressor piston stroke is adjusted by an internal pressure valve. d. Variable displacement compressors control evaporator pressure by varying their pumping capacity.

a

Technician A says mineral oil is compatible with R-12. Technician B says mineral oil is compatible with R-134a. Who is correct?

a

A refrigerant retro fit label must contain all of the following, Except: a. The refrigerant charge amount installed. b. The amount of R-12 removed from the system. c. Name and address of the installer who performed the retrofit. d. The type of refrigerant oil installed and the part number.

b

All of the following statements about system evacuation are true, EXCEPT: a. Vacuum should reach at least 24 to 26 inHg (20.3 to 23.5 kPa absolute) in the first 15 minutes. b. If vacuum does not reach 24 to 26 inHg (20.3 to 23.5 kPa absolute), evacuate for a longer time. c. The longer the evacuation period, the better the moisture removal. d. All systems should be evacuated for a minimum of 30 minutes.

b

Technician A says on some compressors a wobble plate move s pistons. Technician B says some swashplate compressors have double-ended pistons. Who is correct?

both

Technician A says that a liquid antimicrobial deodorizer and disinfectant can be used to eliminate odors in duct systems. Technician B says mold and mildew can be eradicated when it causes a musty odor out of the duct work . Who is correct?

both

Technician A says that a thermostat is used for temperature control in some systems. Technician B says that a low-pressure control is used for temperature control in some systems. Who is correct?

both

Technician A says that the shop that performed the A/C system retrofit must be identified on the retrofit label. Technician B says that the new refrigerant installed must be identified on the retrofit label. Who is correct?

both

Technician A says the pressure cycling switch directly opens and closes the electrical circuit to the compressor clutch coil. Technician B says the pressure cycling switch sends a signal to the microprocessor to turn the compressor on and off. Who is correct?

both

Technician A says the purpose of the pressure cycling switch is evaporator temperature control. Technician B says the purpose of the pressure cutoff switch is system protection. Who is correct?

both

The BILEVEL mode is being discussed. Technician A says air may be directed to the panel and floor in the cooling mode. Technician B says air may be directed to the panel and floor in the heating mode. Who is correct?

both

Vacuum measurement is being discussed. Technician A says the best method is to use an electronic thermistor vacuum gauge. Technician B says a thermistor may use an analog gauge to display vacuum readings. Who is correct?

both

When the A/C system is first turned on a foul smell comes out of the duct system. Technician A says that evaporaor icing could be the cause. Technician B says that mold forming in the evaporator case and on the core could be the cause. Who is correct?

both

If the compressor oil has been drained and it shows signs of metallic particles, all of the following should be done, EXCEPT: a. All system inlet screens should be cleaned after flushing. b. The receiver-drier or accumulator should be replaced after flushing. c. The entire system should be flushed. d. A full charge of heavier refrigeration oil should be added after flushing.

d

An inoperative vacuum motor could be caused by all of the following, EXCEPT: a. defective vacuum switch. b. door cable misadjustment. c. kinked hose. d. leaking reserve tank.

door cable misadjustment.

It is necessary to drain the engine coolant before replacing

heater core

During the compression stroke in a single cylinder of a reciprocating piston compressor, which valve is held closed by pressure?

intake

The retro fit label's background color for R-134a refrigerant is:

light blue

Technician A says mixing two different refrigerants in an air conditioning system is not considered contamination. Technician B says air in an air conditioning system will cause contamination. Who is correct

neither

Technician A says flushing the air conditioning before retrofitting is a common procedure. Technician B says each component should be removed and flushed individually. Who is correct?

neither Check this one

Electronic control heads are being discussed. Technician A says that all units have a connection to use a scan tool or diagnostic tool. Technician B says that different vehicle brands use the same trouble code to indicate the same failure. Who is correct?

neither a or b

Low voltage at the compressor clutch coil could cause

no clutch application or a slipping clutch

In the MAX cooling position the main source of air is from:

recirculated air.

Pressure switches are being discussed: Technician A says that a compressor discharge pressure switch is a low-pressure switch. Technician B says that the pressure switch used for temperature control is a low-pressure switch. Who is correct?​

tech b

Mode door adjustments are being discussed. Technician A says the vacuum motor can be adjusted for motor stroke. Technician B says a cable can be adjusted for full closure of the door. Who is correct?

B

Technician A says on a vehicle equipped with a heater control valve, the valve is found in-line on the heater hose. Technician B says the evaporator may be found inside the engine compartment on some vehicles. Who is correct?

BOTH

Technician A says the purity of refrigerants has been set by SAE purity standards for both R-12 and R-134a. Technician B says refrigerant should test at least 98 percent pure when tested with a purity tester. Who is correct?

BOTH

A customer complains of the passenger compartment temperature always being too hot, cold or not changing as the temperature range is changed on the control panel. On an electronic mode door actuator (motor) system all of the following could cause this problem Except: a. Faulty electronic control head b. Open actuator potentiometer wire c. Faulty actuator d. Open actuator motor wire

OPEN ACUTATOR MOTOR WIRE

During an A/C performance test at 1,500 rpm the compressor will not engage when the A/C switch is moved to the ON position. But if a jumper wire is connected to battery voltage and the compressor connector the clutch engages and operates normally. Technician A says that the A/C switch circuit fuse should be checked. Technician B says that the blower motor relay should be checked. Who is correct?

a

Replacement compressors are being discussed. Technician A says after installing a replacement compressor the receiver drier/accumulator should also be replced. Technician B says the replacement compressor is supplied with oil, and checking the level is not necessary. Who is correct?

a

Technician A says some compressor service procedures can be performed on the vehicle if space permits. Technician B says modern compressors can be removed and reinstalled without discharging the rest of the system. Who is correct?

a

Two technicians are discussing compressor lock-up type failure. Technician A says that during lock-up on a clutchless type compressor the pulley will free-wheel . Technician B says that during lock-up on a conventional type compressor the pulley will free-wheel . Who is correct?​

a

During normal HVAC system operation, system mode doors are a. fully opened. b. fully closed. c. partially closed. d. all of the above, depending on the mode selected.

all of the above, depending on the mode selected.

Electronic actuator motors are being discussed. Technician A says a feedback potentiometer provides a door position signal to the programmer. Technician B says the programmer grounds one side of the energized motor circuit to stop the door movement. Who is correct?

b

The compressor clutch circuit is being tested. Technician A says if the test lamp does not light when connected across the clutch's harness terminals, then the problem is probably a shorted clutch coil. Technician B says a test lamp that flickers or goes out may indicate the PCM or other control device is defective. Who is correct?

b

here are signs of oil spray on the compressor clutch hub and nearby underhood areas. Technician A says that a faulty compressor clutch bearing could be the cause. Technician B says that a leaking compressor shaft seal could be the cause. Who is correct?

b

A customer complains that air flow shifts from the dash vents to the defrost vents during hard acceleration. Technician A says that it could be caused by a misadjusted blend air door. Technician B says this could be caused by a leaking vacuum supply line. Who is correct?

both

Dual zone duct systems are being discussed. Technician A says the passenger controls only the passenger side temperature door. Technician B says the driver may be in control of the rear passenger compartment temperature on some systems. Who is correct?

both

Technician A says a bi-directional scan tool may be used to control the mode doors. Technician B says a positive pressure is usually maintained within the passenger compartment. Who is correct?

both

Technician A says a block or ladder diagrams are used to aid in troubleshooting air conditioning duct system faults. Technician B says the use of test lights is not recommended for under dash service. Who is correct?

both

To measure and adjust compressor clutch air gap, a ____ feeler gauge should be used.

nonmetallic

Technician A says when the compressor oil is drained, the oil can be reused if it looks good. Technician B says the type of new oil installed or added is not important as long as the compressor has enough oil. Who is correct?

niether

All of the following are most commonly removed when the air conditioner is evacuated, EXCEPT: a. refrigerant. b. oil. c. moisture. d. All of the above are removed.

oil

The A/C compressor clutch will not engage but the technician finds normal battery voltage at the compressor clutch connector. Which of the following is the most likely cause?

to great a compressor clutch air gap

The compressor pumps refrigerant as a

vapor

Which of the following desiccants should be used with CFC-12 refrigerant?

xh7 and xh9