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ASE A7 HVAC > Heating, ventilation, A/C and engine cooling system service, diag and repair > Flashcards

Heating, ventilation, A/C and engine cooling system service, diag and repair Flashcards

1
Q

A vehicle is being checked for a lack of cooling concern about two months after another shop replaced the compressor. Tech A says that debris from the old compressor could have clogged the orifice tube. Tech B says that the system could be low on charge due to a leak in the system. Which tech is correct?

A

c

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2
Q

A vehicle came in with a system that was not cooling correctly. A low refrigerant charge caused by a leaking condenser was determined to be the cause. Before the refrigerant was recovered, an identifier was used to check the refrigerant. It was determined that the refrigerant was contaminated. What should the tech do?
A. Recover it into a separate container used for contaminated refrigerant
B. Allow it to escape from the system so it does not contaminate the recovery system
C. Recover and recycle
D. Add new refrigerant to the system and do not recover

A

a

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3
Q

Two techs are discussing leak testing of an air condition system. Tech A says that the blower motor resistor pack can be removed to test evaporator for possible leaks using a leak detector. Tech B says to check the evaporator for leaks at the condensate drain. Which tech is correct?

A

c

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4
Q

An engine runs normally until the A/C is engaged. Then it idles rough and occasionally stalls. What is the most likely cause?
A. A shorted ECT sensor
B. A stuck idle air control (IAC)
C. A clogged orifice tube
D. The A/C system is overcharged

A

b

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5
Q

The A/C system seems to be functioning correctly, but it does not cool as fast or as cold as a similar model. What is the least likely cause?
A. Debris clogged condenser
B. Low on refrigerant charge
C. Partially clogged orifice tube
D. Partially clogged condensate drain

A

d

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6
Q

A lack of cooling is being diagnosed. On an 80 degree day, both low and high pressure gauges read 87 PSI (600 kpa). Tech A says that a clogged orifice tube is the most likely cause. Tech B says that the system is low on refrigerant charge. Which tech is correct?

A

d

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7
Q

A lack of cooling is being diagnosed. The high side pressure is higher than normal and the compressor feels cool when touched. What is the most likely cause?
A. A lack of oil in the system
B. Undercharged with refrigerant
C. Overcharged with refrigerant
D. Clogged or restricted condenser

A

c

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8
Q

The discharge line from the compressor is hot to the touch. Tech A says that the system is low on refrigerant. Tech B says that the compressor is worn and is not compressing the refrigerant enough for proper operation of the A/C system. Which tech is correct?

A

d

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9
Q

An A/C system equipped with a sight glass is being diagnosed. Bubbles (foam) are observed all of the time the system is working with the doors open and the blower fan speed set to high. What is the most likely cause?
A. The system has no refrigerant
B. The system is low on refrigerant
C. The system is overcharged on refrigerant
D. There is water in the system

A

b

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10
Q

A strong pungent odor comes out of the A/C vents. Tech A says that mouthwash should be poured into the air inlet near the windshield to stop the odor. Tech B says that fungicide should be sprayed onto the evaporator to stop the odor. Which tech is correct?

A

b

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11
Q

The tech can test for trapped air (non condensable gases) inside the refrigerant container by ________
A. Checking the outside of the container for frost
B. Checking the pressure versus temperature of the container
C. Weighing the container
D. Sending the container to a special laboratory for analysis

A

b

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12
Q

Tech A says that the refrigerant oil removed during reclaiming should be measured. Tech B says that refrigerant oil can be disposed of with regular engine oil. Which tech is correct?

A

a

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13
Q

Refrigerant should be identified _________
A. After recovery, but before recycling
B. Before recovery
C. Before charging the system
D. After charging the system, but before releasing the vehicle to the customer

A

b

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14
Q

To be sure that all of the moisture in the A/C system has been boiled and removed, a vacuum of at least _______ in Hg should be drawn on the system for at least ___ minutes
A. 28,45
B. 29,60
C. 30,90
D. 30,120

A

a

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15
Q

After the refrigerant has been recovered and recycled, where should it be kept for long-term storage?
A. In a EPA approved container
B. In the recovery machine storage unit
C. In the recycling machine storage unit
D. In a DOT approved container

A

d

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16
Q

What should a tech do before recovering refrigerant from a vehicle?
A. Test it suing a refrigerant identifier and a sealant identifier
B. Connect pressure gauges and check the high and low side pressures
C. Tighten the Schrader valves to be sure they are properly sealed
D. Start the engine and allow the A/C system to work for several minutes

A

a

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17
Q

A tech discovers that 20% of the refrigerant in a vehicle is unknown. What service operation should the service tech perform?
A. Recover and recycle the refrigerant as normal
B. Recover the refrigerant into a container labeled unknown refrigerant
C. Cycle the compressor clutch until the unknown refrigerant is purged from the system
D. Recover the refrigerant and remove the non-condensable gases

A

b

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18
Q

Refer to book

A

a

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19
Q

Refer to book

A

c

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20
Q

An orifice tube type A/C system is being serviced with HFO-1234YF. Which SAE standard recovery, recyling and recharging machine should be used?
A. J1770
B. J2210
C. J2843
D. J2851

A

c

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21
Q

Both high side pressure and low side pressure are low with the engine running and the selector set to the A/C position. Tech A says that the system is undercharged. Tech B says the cooling fan could be inoperative. Which tech is correct?

A

a

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22
Q

A lack of cooling is being diagnosed. A tech discovers that the high pressure line is hot to the touch on both sides of the orifice tube. Tech A says that it is normal operation for an orifice tube system. Tech B says that the orifice tube may be clogged. Which tech is correct?

A

d

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23
Q

Frost is observed on the line between the condenser and the receiver/drier. Tech A says this is normal if the A/C were being operated on a hot and humid day. Tech B says that a restriction in the line or at the outlet of the condenser could be the cause. Which tech is correct?

A

b

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24
Q

Refer to book

A

a

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25
Q

Refer to book

A

d

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26
Q

Refer to book

A

b

26
Q

Refer to book

A

d

27
Q

Refer to book

A

c

28
Q

Tech A says that on an A/C system, the outlet temp of the evaporator and the inlet temp of the evaporator should be about the same if the system is fully charged. Tech B says that the outlet temp will be colder if the system is undercharged. Which tech is correct?

A

a

28
Q

The owner of a vehicle equipped with an orifice tube type A/C system complains that the inside of the vehicle does not cool properly. The A/C compressor clutch constantly cycles on and off whenever the A/C is on. Tech A says that the system is likely low on refrigerant. Tech B says that the most likely cause is an electrical short in the wiring to the A/C compressor clutch. Which tech is correct?

A

a

29
Q

A customer states that the vehicle does not cool as well as it should. Tech A says that the system could be low on charge. Tech B says that if the electric radiator cooling fan is not functioning this can cause a lack of cooling inside the vehicle. Which tech is correct?

A

c

30
Q

Tech A says that some expansion valves can be testing using a CO2 fire extinguisher to check if the cold will cause the valve to close. Tech B says that the operation of the orifice tube can be tested using a CO2 fire extinguisher to cool the orifice tube and watching for a drop in low side pressure. Which tech is correct?

A

a

31
Q

An automotive A/C system is being tested for a lack of cooling complaint. Both high and low pressure are higher than normal. Tech A says that the system is low on charge. Tech B says that the system is overcharged. Which tech is correct?

A

b

32
Q

Tech A says that the low side pressure of the A/C system is best checked for leaks with the engine off. Tech B says that the low side of the system is best checked for leaks when the engine is on and the system is operating. Which tech is correct?

A

a

33
Q

The high side pressure is higher than normal. Tech A says that the compressor may be defective. Tech B says that the condenser may be clogged with leaves or other debris blocking the airflow. Which tech is correct?

A

b

34
Q

A customer complained of a clear liquid leaking from underneath the vehicle on the passenger side after driving for a sort time with the A/C on. The problem only occurs when the A/C is operating. Tech A says the evaporator may be leaking. Tech B says that this may be normal condensed water formed on the cold evaporator coil. Which tech is correct?

A

b

35
Q

Both the low and the high pressure are within normal ranges, yet the inside of the vehicle is not cooling. Tech A says that a partially clogged orifice tube could be the cause. Tech B says that too much refrigerant oil in the system could be the cause. Which tech is correct?

A

b

36
Q

A tech is observing the pressure gauges with the engine off and notices that the high side and low side pressure do not equalize as quickly as they should. Tech A says that the orifice tube may be clogged. Tech B says that the desiccant may be saturated with moisture. Which tech is correct?

A

a

37
Q

A customer states that the carpet on the floor on the passenger side is wet and noticed this when the A/C was first being sued in the spring during damp weather. What is the most likely cause?
A. Evaporator refrigerant leak
B. Clogged evaporator case drain
C. Saturated desiccant in the drier
D. Clogged screen in the accumulator

A

b

38
Q

What two items must be installed or replaced when retorfitting an HFC-134a system to R-1234YF
a. fitting adaptors and a label
b. compressor and o-rings
c. .label and the condenser
d. fitting adaptors and the drier

A

a

39
Q

A thermometer inserted into the A/C vents reads 44 degrees in the ight and center vents but 52 in the left side vent. What is the most likely cause?
a. too much oil charge in the system
b. a partially restricted orifice tube
c. a misadjusted blend door
d. a disconnected air discharge vent tube under the dash

A

d

40
Q

Two techs are discussing if a vehicle is equipped with a r-134a or r-1234yf system. Tech A says that this information should be on an under hood label. Tech B says that the size and shape of the fittings can be used to help determine what refrigerant is in the system. Which tech is correct?

A

c

41
Q

An A/C performance test is being performed. All of the following should be done except ______
a. turn blower to high speed
b. open the doors
c. set controls for max cooling
d. place a thermometer in the inside air inlet door

A

d

42
Q

Two techs are discussing refrigerant oil. Tech A says that PAG oil comes in more than on viscosity and that using the wrong thickness of oil could cause damage to the compressor. Tech B says that refrigerant oil must be kept in a sealed container. Which tech is correct?

A

c

43
Q

After the water pump was replaced and the cooling system refilled with coolant, the heater stopped providing hot air. What is the most likely cause?
a. the wrong concentration of antifreeze was installed
b. an air pocket is trapped in the heater core
c. a defective heater control valve
d. a slipping water pump drive belt

A

b

44
Q

A customer complained that the heat from the heater would come and go and vary with engine speed. What is the most likely cause?
a. defective thermostat
b. low coolant level
c. defective water pump
d. incorrect antifreeze to water ratio

A

b

45
Q

A tech is replacing a water pump. Tech A says that used coolant should be properly disposed of or kept from recycling. Tech B says that the used coolant should be reused to refill the cooling system after the repair is completed. Which tech is correct?

A

a

46
Q

A customer complained of lack of heat from the heater. A check of the cooling system shows that the upper radiator hose is not getting hot. Tech A says that the thermostat may be defective (stuck open). Tech B says that the cause could be a defective (always engaged) thermostat cooling fan. Which tech is correct?

A

a

47
Q

A lack of heat from the heater is being diagnosed. What is the most likely cause?
a. a partially clogged radiator
b. hoses reversed on the heater core
c. partially clogged heater core
d. defective water pump

A

c

48
Q

The temp gauge approaches the red part of the gauge (260 degrees) if driven at slow speeds but does not overheat if driven at highway speed. What is the most likely cause?
a. low coolant
b. incorrect coolant mixture
c. defective water pump
d. inoperative cooling fan

A

d

49
Q

The procedure that should be used when refilling an empty cooling system includes the following:
a. determine capacity, fill halfway with antifreeze and the rest with water
b. fill completely with antifreeze but mix 50/50 solution for the overflow bottle
c. fill block and one half of radiator with 100% antifreeze and fill rest of radiator with water
d. fill the radiator with antifreeze, start the engine, drain the radiator and refill with a 50/50 mixture of antifreeze/water

A

a

49
Q

The coolant in a radiator froze when the temp dropped to -20 degrees. Tech A says that the 100% pure antifreeze in the cooling system could be the cause. Tech B says that too much water in the antifreeze could be the cause. Which tech is correct?

A

c

50
Q

An engine coolant temp is measure to be 210 degrees even though the thermostat specification sheet stat that a 195 unit is installed in the vehicle. Tech A says the thermostat is defective. Tech B says that the radiator is clogged causing the temperature to be higher than normal. Which tech is correct?

A

d

51
Q

Tech A says that the radiator should always be inspected for leaks and proper flow before installing a rebuilt engine. Tech B says that overheating during slow city driving can be due to a defective electric cooling fan. Which tech is correct?

A

c

52
Q

The hot light on the dash is being discussed by two techs. Tech A says that the light comes on if the cooling system temp is too high for safe operation of the engine. Tech B says that the light comes on whenever there is a decrease in cooling system pressure. Which tech is correct?

A

a

53
Q

A customer complains that the heater works sometimes, but sometimes only cold air comes out while driving. Tech A says that the water pump is defective. Tech B says that the cooling system could be low on coolant. Which tech is correct?

A

b

54
Q

A compressor clutch does not engage. Testing confirmed that there is 14 volts at the compressor clutch coil and a good ground connection. What is the most likely cause.
a. low refrigerant oil
b. an open pressure cycling switch
c. a locked up compressor
d. excessive clutch air gap

A

d

55
Q

A cooling system is being refilled following a repair. Tech A says to use conventional green antifreeze (ethylene glycol-based with silicate and phosphate additives) regardless of the type of coolant originally in the system. Tech B says to refill the system with the coolant specified for use by the vehicle manufacturer. Which tech is correct?

A

b

56
Q

The windshield will not defog even though the defroster and/or A/C system seem to be functioning correctly. What is the most likely cause?
a. leaking heater core
b. a leaking evaporator
c. a stuck blend door
d. low on refrigerant

A

a

57
Q

Refer to book

A

c

58
Q

The upper radiator hose collapses when the engine is turned off. What is the most likely cause?
a. defective radiator cap
b. defective upper radiator hose
c. clogged radiator
d. low coolant level

A

a

59
Q

A thermostatic fan clutch is leaking fluid. Tech A says that the unit should be replaced. tech B says that it can cause the engine to overheat. Which tech is correct?

A

c

60
Q

Refer to book

A

c

61
Q

A pressure gauge is installed on the radiator filler neck and the system pressurized to 15 PSI. After a few minutes the pressure was down to 5 PSI according to the gauge on the tester. What is the least likely cause?
a. leaking water pump
b. leaking evaporator
c. leaking radiator hose
d. leaking heat core

A

b

ASE A7 HVAC (3 decks)

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