Term
Tecnician A says that evacuating an A/C system will remove air and moisture from the system.
Technician B says that evacuating an A/C system will remove dirt particles from the system.
Who is right? |
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Definition
The correct answer is A:
Evacuating an A/C system removes air and moisture from the system. The receiver/drier may contain a filter or strainer to catch and trap foreign particles and dirt, but this remains in the receiver/drier and is not removed during the evacuation procedure.
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Term
There is a growling or grumbling noise at the A/C compressor when the system is off and the system is running. The noise stops when the system is turned on.
Technician A says that a bad compressor bearing could be the cause. Technician B says that bad compressor clutch bearing could be the problem.
Who is right? |
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Definition
| The correct answer is technician B. The compressor clutch bearing allows the rotor/pulley assembly to spin indepently of the compressor shaft when the A/C system is off. When the engine is running and the A/C system is off, the compressor clutch bearing is spinning. When the A/C system is turned on, the rotor/pulley assembly and the armature are locked together by magnetic action of the compressor clutch coil. |
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Term
Your low pressure gauge is reading about 10 psi your high pressure is reading about 95 psi.
With those readings taken with the A/C system operating at oustide temperature of 85F(29C), what do the readings indicate?
A. normal operation
B. low refrigerant level
C. a restriction in the high side
D. damaged compressor |
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Definition
The correct answer is B.
Low pressure on both the low side and the high side indicates indicates a low refrigerant charge. |
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Term
Recovery/recycling equipment must have shutoff valves located within 12-in. of the hoses' service ends so that:
A. oil can be added to the refrigerant
B. the unit can be isolated from the refrigerant source
C. the filter can be changed without disconnecting the hoses
D. Refrigerant discharge can be kept to a minimum. |
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Definition
The correct answer is D:
According to the Clean Air Act, recovery/recycling equipment must have shutoff valves located within 12-in. of the hoses' service ends so that refrigerant disharge to the atmosphere can be kept to a minimum. |
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Term
When recovering refrigerant for an A/C system, how long should the technician wait after recovery/recycling unit has been turned off to see if there is any residual pressure in the system.
A. 1 minute
B. 5 minutes
C. 10 minutes
D. 15 minutes |
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Definition
The correct answer is B.
The technician should wait five minutes and watch the gauges to see if there is any residual pressure. If there is, repeat the process to remove any remaining refrigerant until the A/C system holds a stable vacuum for at least five minutes. |
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Term
A system with low pressure on the low side and heavy frost accumulation on the inlet side od the Thermostatic Expansion Valve (TXV) indicates a:
A. TXV valve stuck open
B. clogged condensor
C. defective compressor
D. clogged screen or TXV stuck closed |
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Definition
The correct answer is D.
A low pressure reading on the low side and a heavy frost accumulation on the inlet side of the TXV indicates a clogged screen at the expansion valve inlet or a stuck closed. |
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Term
A blower motor only works on high speed. Which of the following causes is the MOST LIKELY?
A. defective blower relay
B. defective blower resistor
C. defective blower switch
D. blown fuse or tripped circuit breaker |
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Definition
The correct answer is B.
Answer D is incorrect because if the blower fuse was blown or circuit breaker tripped, the blower would not work at all. Answer A is incorrect because a blower relay is generally only used for the high blower speed and this is working. Answer C, the blower switch is a possible cause but the most likely cause for operation on only high speed is that a portion of the resistor assembly is burned out. |
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Term
A customer complains that when accelerating his car with the A/C on, the cold air flow from the dash outlets shifts to the floor. Technician A says that this is caused by a faulty check valve in the vacuum reservoir. Technician B says that this condition is due to a vacuum leak. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B |
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Definition
The correct answer is C.
Both technicians are right. If during hard accelration, air routing changes by itself, it's probably due to a leak in the system or a faulty check valve in the vacuum reservoir. A complaint that the mode shifts from the dash the floor at wide-open throttle is evidence that the system isn't holding vacuum. |
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Term
When pressure testing the cooling system on a late model gasoline engine vehicle, the pressure on the tester drops but no leks can be found in the engine compartment. Technician A starts the engine and, seeing the pressure on the tester gauge increase, says that there is an internal leak, a blown head gasket.
Technician B says that there cannot be an internal leak because the engine oil looks normal, not milky like it would be if coolant were present, and there is no white smoke coming from the exhaust pipe. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
d. Neither A or B |
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Definition
The correct answer is A.
If the engine is started while pressure testing a cooling system and the pressure immediately increases, there could be a head gasket leak, but not into the crankcase. The coolant may be going out of the tailpipe, but since this a late model gasoline engine vehicle and equipped with a catalytic convertor, there is no white smoke from the exhaust because the convertor super-heats the coolant into such a fine vapor that it is not noticeable. |
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Term
When identifying an A/C system, Technician A says that an accumulator located between the evaporator and compressor is an indication that the system has an orfice tube. Technician B says that when the High-side service port fitting is smaller than the one on the low side, the system uses r134a refrigerant. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A and B |
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Definition
The correct answer is A.
Systems using an expansion valve have a receiver/drier between the valve and condensor, while orfice tube systems have an accumulator between the evaporator and compressor. Technician B is wrong because on R134a systems, the low-side service port is the smaller one. |
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Term
When troubleshooting an ATC system, the system responds when ambient and in-vehicle temperature sensors are heated and cooled. However, there is no response when the sunload sensor is exposed to a light source. Techician A says that the porblem is with the sustem's programmer. Technician B says that the problem is with the sunload sensor. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B |
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Definition
The correct answer is B.
If the system reacts with a change to one or two inputs but not the third, the problem is most likely confined to the single sencor or its circuit. But if no reaction is observed on any of the units, or only a parial reaction is seen, the problem is usually with the programmer. |
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Term
The following are all methods of orfice tube replacement EXCEPT:
A. Replace the line that incorporates the orfice tube.
B. Disconnect the liquid line from the evaporator inlet line and oull the orfice tube straight out with an extractor tool.
C. Disconnect the liquid line from the evaporator inlet line and, using a twisting motion to break free of the line, pull out the orfice tube with an extractor tool.
D. Cut out the section of line that contains the orfice tube and, using a kit, install a new orifice tube line segment.
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Definition
The correct answer is C.
When removing the orifice tube with an extractor tool, do not twist or rotate the orifice tube in the line as it can break. If an orifice tube during removal, special tools are available to extract broken orifice tubes. All of the other answers are methods of orifice tube replacement. |
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Term
When converting the A/C system in an older vehicle to R134a refrigerant, what percentage of the original R12 charge amount should be used?
A. 75 percent
B. 100 percent
C. 99 percent
D. 80-90 percent |
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Definition
The correct answer is D
When charging a retrofitted system with R134a refridgerant, the sytem will only require 80 - 90 percent of the original R12 charge amount. |
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Term
A vehicle with R134a refridgerant in the A/C system has a refridgerant leak. Technician A says that a propane gas leak detector should be used to find the location of the leak. Technician B says that an electronic leak detector shgould be used to check for leaks. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A or B |
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Definition
The correct answer is B
Technican A is wrong because propane gas leak detectors cannot detect R134a. technician B is right, but he must make sure the electronic leak detector is designed for R134a, as many older units are not. |
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