Practice Test Flashcards
Technician 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?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
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 process.
There is a growling or rumbling noise at the A/C compressor when the system is off, and the engine 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 a bad compressor clutch bearing could be the cause. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
The correct answer is B.
The compressor clutch bearing allows the rotor/pulley assembly to spin independently 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 the magnetic action of the compressor clutch coil.
A/C gauges show lower than normal pressure on both the low side and the high side with the A/C system operating. What do the readings indicate?
A. Normal operation
B. Low refrigerant level
C. A restriction in the high side
D. Damaged compressor
The correct answer is B.
Low pressure on both the low side and the high side indicates a low refrigerant charge.
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.
The correct answer is D.
According to the Clean Air Act, recovery/recycling equipment must have shutoff valves located within 12 inches (30 cm) of the hoses’ service ends so that refrigerant discharge to the atmosphere can be kept to a minimum.
When recovering refrigerant from an A/C system, how long should the technician wait after the recover/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
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.
A system with a low pressure on the low side and a heavy frost accumulation on the inlet side of the TXV indicates a:
A. TXV stuck open
B. Clogged condenser
C. Defective compressor
D. Clogged screen or TXV stuck closed
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 TXV stuck closed.
A blower motor only works on high speed. Which of the following causes is MOST LIKELY?
A. Defective blower relay
B. Defective blower resistor
C. Defective blower switch
D. Blown fuse or tripped circuit breaker
The correct answer is B.
A blower relay is generally only used for the high blower speed and this is working. 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. If the blower fuse was blown or circuit breaker tripped, the blower would not work at all.
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 nor B
The correct answer is C.
If, during hard acceleration, 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 to the floor at wide-open throttle is evidence that the system isn’t holding vacuum.
When pressure testing the cooling system on a late model gasoline engine vehicle, the pressure on the tester drops but no leaks 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 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 nor B
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 the tailpipe, but since this is a late model vehicle equipped with a catalytic converter, there is no white smoke from the exhaust because the converter super-heats the coolant into such a fine vapor that it is not noticeable.
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 orifice 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 nor B
The correct answer is A.
Systems using an expansion valve have a receiver drier between the valve and condenser, while orifice 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.
When troubleshooting an ATC system, the system responds when the 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.
Technician A says that the problem is with the system’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 nor B
The correct answer is B.
If the system reacts with a change to one or two inputs but not to the third, the problem is most likely confined to the single sensor or its circuit. But if no reaction is observed on any of the units, or only a partial reaction is seen, the problem is usually with the programmer.
The following are all methods of orifice tube replacement EXCEPT:
A. Replace the line that incorporates the orifice tube.
B. Disconnect the liquid line from the evaporator inlet line and pull the orifice tub 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 orifice tube with an extractor tool.
D. Cut out the section of line containing the orifice tube and, using a kit, install a new orifice tube line segment.
The correct ans
Technician A says when there is a “U” DTC, it should be repaired before any further diagnostics can be performed. Technician B says “U” DTCs indicate there is nothing wrong with the A/C system. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
A vehicle with R134a refrigerant in the A/C system has a refrigerant 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 should 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 nor B
Which of the following is a true statement regarding R134a 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 a lower pressure than R12
The compressor in an A/C system does not run. When a jumper wire is used to connect the battery positive terminal to the power connector, the compressor clutch engages.
Technician A says that the clutch coil is defective. Technician B says that the pressure cycling switch could be defective. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
The floor inside a vehicle is wet and there is a slimy film on the windows.
Technician A says that the heater core is leaking. Technician B says that the evaporator case drain plug is clogged. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
During A/C system operation, a knocking sound can be heard coming from the compressor.
Technician A says that there could be internal compressor damage. Technician B says that the compressor mounting brackets and bushings should be checked. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
All of the following could cause poor heater performance EXCEPT:
A. Defective temperature blend door actuator
B. Radiator coolant temperature below 150F
C. Heater core return hose much cooler than inlet hose
D. Stuck open heater control valve
During an A/C system performance test, the air temperature at the center outlet duct is warm to slightly cool and the low-side and high-side pressures on the manifold gauge set are both low. All of the following could be the cause of these symptoms EXCEPT:
A. Clogged orifice tube
B. Expansion valve stuck closed
C. Restricted receiver drier
D. Plugged condenser
What is the minimum system pressure necessary to leak test with an electronic leak detector?
A. 25 psi
B. 50 psi
C. 75 psi
D. 100 psi
Observing the data stream while operating a HVAC system on a late model vehicle the counts for the blend door change when the vehicle is moved outside in the mid day sun. Technician A says there is an intermittent problem with the blend door actuator that will eventually set a DTC. Technician B says that under no circumstances should the counts change on the blend door motor. Who is correct?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
When diagnosing an ATC system, most of the system temperature sensors can be tested for:
A. Resistance and current flow
B. Resistance and voltage drop
C. Voltage drop and current flow
D. Current flow and continuity
During an A/C system performance test, high-side pressure was found to be excessive and the A/C compressor continued to run.
Technician A says that the high-pressure cutout switch could be defective. Technician B says that there could be an air flow obstruction at the condenser. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
The A/C compressor cycles rapidly, and air coming from the vents is only slightly cool.
Technician A says the problem could be a low refrigerant charge. Technician B says the problem could be a defective thermostatic switch. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
To properly evacuate an A/C system, the vacuum pump should be operated a minimum of:
A. 5 minutes
B. 10 minutes
C. 20 minutes
D. 30 minutes
Technician A says that a special tool is required to disconnect and connect spring lock fittings. Technician B says that when assembling new spring lock fittings, new O-rings lubricated with clean refrigerant oil should be used. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
All of the following are true statements concerning in-line filters EXCEPT:
A. They are usually installed in a system that has suffered a compressor failure
B. They are installed to protect the new compressor from metal chips or other debris that could be in the system from the original compressor failure
C. They are installed to collect debris that could clog the orifice tube or expansion valve filters
D. Filters are only installed in the high side of the system
Two technicians are discussing sight glass observations. Technician A says that if foam is seen in the sight glass, the refrigerant charge is low. Technician B says that if oil streaks are seen in the sight glass, the refrigerant charge is low. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
Technician A says that moisture in an A/C system can freeze in the expansion valve and stop the system from cooling. Technician B says that moisture in the A/C system will react with R12 to form an acid that can cause corrosion. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
Low heater output can be caused by all of the following EXCEPT:
A. An engine low on coolant
B. A stuck open cooling system thermostat
C. A restricted heater control valve
D. A disengaged clutch type radiator fan
The high-side pressure in an A/C system is above specifications. All of the following could cause this problem EXCEPT:
A. An overcharge of refrigerant
B. Restricted air flow across the condenser
C. A slipping fan belt
D. A broken compressor reed valve
When filling a container with recycled refrigerant, to what percentage of the container’s gross weight rating should it be filled?
A. 50 percent
B. 60 percent
C. 70 percent
D. 80 percent
A vacuum door actuator is being tested. When vacuum is applied with a handheld vacuum pump, the door does not move and the reading on the vacuum gauge is zero.
Technician A says that the door does not move because it is binding or obstructed. Technician B says that the door does not move because the actuator is defective. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
A customer complains of a foul odor coming from the dash outlets whenever the A/C and blower are on.
Technician A says that this is caused by a clogged evaporator drain. Technician B says that this is caused by bacterial growth on the evaporator. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
When an A/C system is operating, a clicking or buzzing noise is heard coming from the compressor.
Technician A says that this noise means that the system is overcharged. Technician B says that the noise could be due to air in the system. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
A customer complains that when parallel parking, his car repeatedly stalls, but only when the air conditioning is on.
Technician A says that the power steering pressure switch is defective. Technician B says that there is a problem with the power steering pump. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
All of the following are true statements about receiver 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
Technician A says that the pressure cycling switch is usually located on the accumulator. Technician B says that the refrigerant must be recovered from the system before the switch can be removed. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
Technician A says that the A/C system can be charged through the high or low side only when the engine is not running. Technician B says that the A/C system can charge through the low side when the engine is running. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
An air conditioning check has uncovered a discharge in the system and compressor damage.
Technician A says that after the repairs are made, to check the low-pressure cutoff switch. Technician B says lubricating oil is carried by the refrigerant through the system. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
When checking recycled refrigerant for excess non-condensable gases (air), Technician A says that the container must be stored at 65F or above for 8 hours out of direct sunlight, before checking the pressure. Technician B says if the pressure is higher than the limit shown for a given temperature, there is air in the tank. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
The operation of the thermostatic switch depends on the temperature of the:
A. Condenser
B. Compressor
C. Evaporator
D. Outside air
All of the following are causes for fan clutch replacement EXCEPT:
A. Oil film on the back of the clutch
B. No viscous drag
C. Fan speed does not increase as engine warms up
D. When engine is hot, fan stops spinning in only two seconds after shut down
Technician A says that an ambient temperature switch protects the compressor from damage. Technician B says that an ambient temperature sensor provides input for the Automatic Temperature Control (ATC) system. Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
If a capillary tube were to break at some point between its sensing bulb and the expansion valve, what affect 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 effect on the expansion valve
