Climate Control ASE Prep
The blower motor speed is believed to be slow at all speeds. It is determined that the blower will not reach full speed when on high. The voltmeter is reading 8 volts in the high-speed switch position. Technician A says the cause could be low source voltage. Technician B says the problem could be a high resistance at the blower motor ground. Who is correct?
Both A and B (the blower motor voltage drop on high speed should be near system voltage. A high resistance fault at the ground could cause voltage to be dropped at the ground circuit)
During refrigerant recovery, a cylinder is considered full when it reaches what capacity? 50 percent 60 percent 70 percent 80 percen
60 percent
Technician A says a loose ground wire may be the cause of no blower operation. Technician B says a no blower operation may be caused by a defective compressor clutch diode. Who is correct? A only B only Both A and B Neither A nor B
A Only
The filter screen of an orifice tube is covered with aluminum particles. Which of these could be the cause? A leaking desiccant bag A plugged condenser A damaged compressor A damaged evaporator
A damaged compressor
In the electric cooling fan , the low-speed and high-speed fans do not operate when the engine is overheated. Both fans will run when the air conditioning is turned on. The cause of this problem could be: a blown 10A, 5C fuse in the instrument panel fuse block. a defective engine coolant temperature sensor. a defective high-speed coolant fan relay. a defective A/C pressure fan switch.
A defective engine coolant temperature sensor (coolant sensors send a varying voltage to logic devices as temperature changes take place in the engine).
An A/C system has a vacuum reservoir, a check valve, and a vacuum-operated mode door actuator including the blend air door. While operating in the A/C mode and climbing a steep hill with the throttle nearly wide open, the air discharge temperature gradually becomes warm, and the air discharge switches from the panel to the defrost ducts. The A/C system operates normally under all other conditions. The cause of this problem could be: a leaking panel door vacuum actuator. a defective vacuum reservoir check valve. a leaking blend air door vacuum actuator. a leaking intake manifold gasket.
A leaking vacuum reservoir check valve (will not trap the vacuum, possibly causing the mode doors to change positions)
When a fixed orifice tube (FOT), cycling clutch A/C system is operating at 82°F (27.8°C) ambient temperature, the compressor clutch cycles several times per minute and the evaporator outlet line is warm. The high-side gauge shows lower-than-normal pressures. There is no frost on any of the A/C system components. The cause of this problem could be: a low refrigerant charge. a flooded evaporator. a restricted accumulator. an overcharge of refrigerant.
A low refrigerant charge (may cause faster than normal clutch cycling)
A vehicle has a problem of a musty smell being produced by the HVAC system when the blower is turned on. Which of these would most likely cause this problem? A leaking heater core A moldy substance growing on the evaporator core An A/C system low on refrigerant A shorted out blower resistor
A moldy substance growing on the evaporator core
A vehicle with blended refrigerant is being repaired. Technician A says that the refrigerant can be recovered with a machine set up for this type of refrigerant. Technician B says that this refrigerant can be safely reused to recharge other vehicles. Who is correct? A only B only Both A and B Neither A nor B
A only
While diagnosing the cause of a blown fuse in the blower motor circuit, Technician A says a short in the circuit could have caused the fuse to blow. Technician B says an open field winding in the fan motor could have caused the fuse to blow. Who is correct? A only B only Both A and B Neither A nor B
A only
A check of the A/C system with a manifold and gauge set indicates that after 15 minutes of operation, the low-side gauge shows a pressure of 10 psi. Technician A says the cause could be a faulty compressor cycling switch. Technician B says that the fixed orifice tube may be clogged. Who is correct? A only B only Both A and B Neither A nor B
A only ( A stuck closed compressor cycling switch would cause low side pressure to be lower than normal due to the system constantly running. The sensor should open at around 20/25 psi)
Technician A says that the receiver dryer can be incorporated into the condenser on vehicles that use a thermal expansion valve. Technician B says that the condenser can be effectively flushed if the passages become blocked with foreign material. Who is correct? A only B only Both A and B Neither A nor B
A only (Receiver dryer is located on exit side of the condenser)
An A/C compressor cycles off when the high-side pressure builds. Technician A says that the high-pressure cutoff switch is opening the circuit to the compressor clutch. Technician B says that the pressure release valve is opening the circuit to the compressor clutch. Who is correct? A only B only Both A and B Neither A nor B
A only (The high side pressure switch is wired with the compressor clutch in series. Designed to open and disengage the clutch at 350 to 375 PSI. Reengages at 250 PSI)
The engine overheats when the vehicle is parked, with the engine running. When the vehicle is driven at highway speeds, the engine operates at the normal temperature. Technician A says a missing or broken radiator fan shroud could be the cause. Technician B says a seized thermostatic fan clutch could be the cause. Who is correct? A only B only Both A and B Neither A nor B
A only (a fan clutch being locked would not cause overheating, this would cause over cooling)
Technician A says the lines before and after the receiver/drier should be the same temperature. Technician B says the lines before and after the condenser should be the same temperature. Who is correct? A only B only Both A and B Neither A nor B
A only (as the refrigerant in the condenser releases heat, it changes state and the outlet should be cooler than the inlet)
A receiver-drier is located between the condenser and the evaporator. Technician A says the receiver-drier should be changed if the outlet is colder than the inlet. Technician B says the receiver-drier should be changed if the refrigerant in the sight glass appears red. Who is correct? A only B only Both A and B Neither A nor B
A only (if the outlet is colder than inlet than the unit is restricted)
Frost is forming on one of the condenser tubes near the bottom of the condenser. This problem could be caused by: restricted airflow passages in the condenser. a refrigerant leak in the condenser. a restricted refrigerant passage in the condenser. a restricted fixed orifice tube.
A restricted refrigerant passage in the condenser.
Hybrid vehicles can have any of these HVAC system characteristics EXCEPT: a vacuum controlled blend air door. an electric A/C compressor. a PTC heater core. orange high voltage wires under the hood.
A vacuum controlled blend door
Which of these methods would be the LEAST LIKELY routine when calibrating an ATC climate control system after a blend actuator was replaced? Depressing a sequence of buttons on the digital climate control head Adjusting the temperature control to the full hot position for 2 minutes Running a calibration with a factory scan tool Running a calibration with a generic scan tool
Adjusting the temperature control to the full hot position for 2 minutes
A refrigerant identifier can tell if there is: air in the refrigerant system. an excessive refrigerant charge. excessive oil in the refrigerant system. a low refrigerant charge.
Air in the refrigerant system
Any of these statements about A/C recovery/recycling equipment are true EXCEPT: The equipment label must indicate UL approval. The equipment label must indicate SAE J1991 approval. Any size and type of refrigerant storage container over 10 pounds (4.8 kg) may be used in this equipment. R-12 and R-134a refrigerants or refrigerant oils must not be mixed in the recovery/recycling process.
Any size and type of refrigerant storage container over 10 pounds may be used in this equipment
A car makes a hissing noise each time the A/C system and engine are turned off. Technician A says that the noise is caused by a refrigerant leak. Technician B says that the noise is caused by equalization of system pressures. Who is correct? A only B only Both A and B Neither A nor B
B only
Technician A says a high-side charging procedure should be completed with the engine running. Technician B says if liquid refrigerant enters the compressor, damage to the compressor may result. Who is correct? A only B only Both A and B Neither A nor B
B only
Technician A says that the oil level of some late-model compressors may be checked with the use of a dipstick. Technician B says the oil must be drained from some compressors and measured in a graduated container. Who is correct? A only B only Both A and B Neither A nor B
B only
The blower motor is totally inoperative on a late model vehicle equipped with automatic temperature control. The technician tests the circuit and finds a variable pulse width voltage pattern on the blower motor signal circuit. Technician A says that the blower motor relay could be defective. Technician B says that the blower motor ground could be faulty. Who is correct? A only B only Both A and B Neither A nor B
B only (A brushless DC blower motor does not use a relay to send voltage to the blower motor)
(high side - 300/350. Low side - 30-45) the readings on the gauges in the figure were taken on a TXV system that uses R-134a on a 78-degree day after 12 minutes of A/C operation. Technician A says that these readings are normal for the temperature and conditions. Technician B says that these readings could be caused by a refrigerant overcharge. Who is correct? A only B only Both A and B Neither A nor B
B only (normal pressures on a 78* day would be 25/30 on low side and 150/175 high side)
The vacuum check valve was lost in a previous repair, but the remaining hoses were still connected. Technician A says that the mode doors would be stuck in the heat mode and would not move in any other positions. Technician B says that the mode actuators would work normally until the vehicle drove up steep hills. Who is correct? A only B only Both A and B Neither A nor B
B only (the HVAC system would still operate normally until a low-vacuum situation such as driving up steep hills that require high throttle angles).
Which of these sensors would be LEAST LIKELY available to view on a scan tool during the diagnosis of an HVAC problem on a vehicle equipped with ATC? Blend door actuator position sensor voltage Mode door actuator position sensor voltage Cabin air temperature voltage Blower motor amperage
Blower motor amperage (blower motor amperage is not typically a value that is displayed on a scan tool. A digital meter with an amp clamp could be used to measure this value)
A customer complains that the air-conditioning system cools satisfactorily during the early morning or late evening, but does not cool during the hot part of the day. During testing, the low-side gauge starts out reading normal, then drops into a vacuum. Technician A says that ice could be forming on the expansion valve. Technician B says that the drier could be saturated with moisture. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
A gurgling noise is heard inside the passenger compartment. The noise is coming from the A/C heater case. Technician A says the heater core coolant passages may be restricted. Technician B says the coolant level in the cooling system may be low. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
A mode actuator is being diagnosed on a late-model vehicle. Technician A says that a test light could be used to measure the voltage supplied to the actuator. Technician B says that a digital storage oscilloscope (DSO) could be used to detect an intermittent electrical fault at the actuator. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
A vehicle is being diagnosed for an A/C problem and the identifier revealed that there is 4% air in the refrigerant system. Technician A says that this problem could have been caused by the failure of evacuating the A/C system during a repair operation. Technician B says that this system will need to be recovered and then evacuated for at least 30 minutes. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
A vehicle with rear heat and air has a rear heater that does not get warm enough. Technician A says that a partially collapsed heater pipe could be the cause. Technician B says that a partially blocked rear heater core could be the cause. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
An A/C system is being leak tested. Technician A carefully checks all system connections and says the presence of oil around the fitting of an A/C line or hose is an indication of a possible refrigerant leak. Technician B uses a hand-held electronic leak detector and moves the hose slowly along all components of the refrigerant system. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
An air-conditioning clutch does not engage the compressor. A voltage measurement shows there is 12 volts at the clutch coil feed wire. Technician A says that the clutch coil could be bad. Technician B says that the clutch coil ground could be bad. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
Automatic temperature control (ATC) A/C systems are being diagnosed. Technician A says that some systems have to be recalibrated after the vehicle battery is replaced. Technician B says that these systems use a sun load sensor to calculate radiant heat load. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
None of the vacuum controls are operational with the engine running at idle speed. Technician A says the problem could be caused by a disconnected vacuum supply hose. Technician B says the manifold vacuum fitting may be blocked. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
Technician A says a vacuum pump is used during the recovery process to remove the last trace of refrigerant from the system. Technician B says any air or moisture not evacuated from the A/C system reduces the system's efficiency. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
Technician A says that a restricted cabin air filter can cause reduced airflow at all of the duct outlet locations. Technician B says that the cabin air filter should be inspected during routine preventative maintenance activities on a vehicle. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
Technician A says that the evaporator housing and water drain are integral parts of the evaporator housing assembly. Technician B says that a crack or break in the housing may reduce the cooling capacity of the air conditioner. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
Technician A says the desiccant in a receiver/drier absorbs moisture and it can become quickly contaminated if exposed to atmosphere. Technician B says orifice tube systems use an accumulator to store excess refrigerant and to filter and dry the refrigerant. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
The air passages through an A/C condenser are severely restricted. Technician A says this may cause refrigerant discharge from the high-pressure relief valve. Technician B says this may cause the high-side pressure and low-side pressure to be higher than normal. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
The inside of the windshield has a sticky film. Technician A says the engine coolant level should be checked. Technician B says the heater core may be leaking. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
There is oil residue around the high-pressure relief valve and the A/C refrigerant charge has been determined to be low. Technician A says the cause could be restricted air passages through the condenser. Technician B says the refrigerant system may have been overcharged. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
While conducting an A/C system performance test, Technician A says to insert a thermometer into the air duct at the center of the dash and monitor discharge temperature. Technician B says to perform a visual inspection. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
While diagnosing higher-than-normal-system pressures, Technician A checks the condenser for dirt buildup in the condenser's fins. Technician B tests the engine for indications of an overheating condition. Who is correct? A only B only Both A and B Neither A nor B
Both A and B
Technician A says that some A/C systems control evaporator pressure by varying the displacement of the compressor. Technician B says some systems regulate the flow of refrigerant into the evaporator with a thermal expansion valve (TXV). Who is correct? A only B only Both A and B Neither A nor B
Both A and B (VDC used on high side to control refrigerant pressure and evaporator (suction) pressure on low side)
A vehicle is being diagnosed for poor heater performance. Technician A says that a stuck open thermostat could be the cause of this problem. Technician B says that a restricted heater core could be the cause of this problem. Who is correct? A only B only Both A and B Neither A nor B
Both A and B (a stuck open thermostat will cause the engine to fail to reach normal operating temperature.)
(High - 100/125, Low - 45/75), the gauge readings were taken on a CCOT system that uses R-134a on an 85-degree day after the A/C system had run for about 10 minutes. Which of these is the most likely cause of the readings shown? Refrigerant is overcharged Restricted airflow at the condenser Damaged compressor reed valves Refrigerant is undercharged
Damaged compressor reed valves
A vehicle with ATC has an inoperative blower motor. The technician used a scan tool to troubleshoot the problem and found that the blower would work at all commanded speeds when using the output test on the scan tool. Which of these faults is the most likely cause for this problem? Open circuit on the blower motor ground Cabin temperature sensor shorted out Faulty ATC control panel assembly Blown blower motor fuse
Faulty ATC control panel assembly
An A/C system equipped with an accumulator is a: thermostatic expansion valve system. fixed orifice tube system. receiver-drier system. suction throttling valve system
Fixed Orifice tube system (TXV/Receiver dryer FOT?Accumulator)
Which of these would NOT be used to detect an A/C refrigerant leak on an R-134a system? Flame-type leak detector Halogen leak detector Dye and UV light Audible noise from the leak
Flame type leak detector
This device could not be a high side switch because it is mounted on the low side of the system at the accumulator... low-pressure switch. high-pressure cutoff switch. cycling clutch switch. low refrigerant charge switch
High pressure cutoff switch (All the others mount to accumulator)
While conducting a pressure test on an A/C system, the ambient temperature is 80°F (26.6°C), the low-side gauge reads low (8 psi), and the high side also reads low (85 psi). Which of these could cause these readings? Low refrigerant level Normal operation Bad compressor A high-side restriction
Low refrigerant level
Evacuating a refrigerant system removes: moisture from the system. rust from the system. dirt from the system. desiccant particles from the system.
Moisture from the system
Which of these is LEAST LIKELY to be performed during an A/C system recovery procedure? Refrigerant is removed from a vehicle. Refrigerant is filtered by the recovery machine. Most of the A/C system oil is removed the vehicle. Refrigerant is weighed by the recovery machine
Most of the A/C system oil is removed from the vehicle
Condenser airflow is being diagnosed. Technician A says a slipping fan clutch will reduce ram airflow. Technician B says reduced airflow across the condenser results in low suction pressure. Who is correct? A only B only Both A and B Neither A nor B
Neither A or B
Technician A says that new replacement compressors must always have oil added to them before installing on the vehicle. Technician B says that all R134a compressors use the same lubricating oil. Who is correct? A only B only Both A and B Neither A nor B
Neither A or B
Technician A says the R-12 refrigeration system does not need to be depressurized to replace the high pressure relief valve. Technician B says if replacing the high pressure relief valve on a retrofitted to R-134a system, it is necessary to replace it with one that has the same relief pressure specification as the original relief valve. Who is correct? A only B only Both A and B Neither A nor B
Neither A or B (Replace high pressure relief valve with a high pressure cut out switch when retrofitting.)
Technician A says that a faulty A/C pressures sensor can be bypassed with a fused jumper wire to make the compressor operate. Technician B says that a faulty evaporator temperature sensor can be bypassed with a fused jumper wire to make the compressor operate. Who is correct? A only B only Both A and B Neither A nor B
Neither A or B (sensors must be diagnosed with scan tools and meters)
Which of these oils is the standard oil used by OEMs in R-134a systems? Mineral oil CCOT Ester oil PAG
PAG
When interpreting gauge readings, an elevated high-side reading may be caused by any of these EXCEPT: refrigerant overcharge. restricted airflow to the condenser. poor airflow across the evaporator. a slipping fan clutch.
Poor airflow across evaporator (would lower high side pressure since little heat is added to the refrigerant)
Any of these methods of R-134a A/C system leak detection are acceptable EXCEPT: dye and black light. electronic leak detector. ultrasonic detector. propane burner
Propane Burner
Evacuating the A/C system involves which of these? Removing the oil from the system Removing the refrigerant and storing in a safe captured system Pressurizing the system with nitrogen for leak testing purposes Pulling the system into a negative pressure to remove the air and moisture
Pulling the system into a negative pressure to remove the air and moisture
Which of these procedures is LEAST LIKELY to be done during an electric A/C compressor replacement on a hybrid vehicle? Remove the battery circuit breaker Replace the compressor belt Use ester based oil in the A/C system Use a CAT III meter for voltage measurements
Replace the compressor belt
An A/C system is being tested with pressure gauges. The high-side pressure is low, and the low-side pressure is high. Which of these is the LEAST LIKELY cause of these pressures? Damaged compressor reed valves Restriction in the high side of the system Leaking compressor head gasket Incorrectly mounted POA or STV
Restriction in the high side of the system
Any of these statements are true about using the tool shown in the figure (refrigerant line - orifice tube - service tool) to remove an orifice tube assembly EXCEPT: Pour a small amount of refrigerant oil on top of the orifice tube to lubricate the O-rings. Rotate the T-handle to engage the notch in the tool in the orifice tube tangs. Rotate the T-handle to remove the orifice tube from the evaporator inlet pipe. Hold the T-handle and rotate the outer sleeve on the tool to remove the orifice tube.
Rotate the T-handle to remove orifice tube from the evaporator inle pipe
Any of these could be the result of a calibration problem in the ATC system EXCEPT: the air temperature is warm when it should be cold. the air is distributed from the vent when it should be coming from the floor. the A/C compressor will not engage even when full cool is commanded at the control head. the air is distributed from the defrost when it should be coming from the vent.
The A/C compressor will not engage even when full cool is commanded at the control head
A technician finds that an air-conditioning system has excessive high-side pressure. The low-side pressure is normal to high. A probable cause of this problem is: the condenser air passages are restricted. a leaking thermostatic expansion valve. an open bypass valve. a malfunctioning compressor reed valve.
The condenser air passages are restricted
Following a heater core replacement, a vehicle has a problem with a fluctuating temperature gauge while driving. Which of these could be the cause of this problem? The temperature sending unit needs to be replaced. The cooling system has air trapped in it and needs to be bled. The wrong type of coolant was installed. The heater control valve is malfunctioning.
The cooling system has air trapped in it and needs to be bled (Improper filling process)
The A/C line entering the receiver dryer is very warm and the line exiting the receiver dryer is cool. Which of these could cause this condition? The system is overcharged. The receiver dryer is restricted. The system is undercharged. The TXV is stuck open.
The receiver dryer is restricted. (Inlet and outlet temp should be close to the same in dryer).
A refrigerant storage container is being tested for static pressure with a manifold gauge and it has been in a 70 degrees (f) room for 6 hours. The pressure in the container is 94 psi. Which of these is LEAST LIKELY to cause this result? The refrigerant has a 5% mixture of air blended with it. The refrigerant has foreign chemicals blended with it. The refrigerant has an 8% mixture of air blended with it. The refrigerant container is overfilled by 1%.
The refrigerant container is overfilled by 1%
After the recovery process, the low-side pressure increases above zero after 5 minutes. This condition indicates: there is still some refrigerant in the system. there is excessive oil in the refrigerant system. the refrigerant system is leaking. there is excessive moisture in the refrigerant system.
There is still some refrigerant in the system
The high-side pressure on a system with a cycling clutch and pressure cycling switch is 245 psi, the low-side pressure hovers around 28 psi, and the ambient temperature is 98°F (36.6°C). What do these gauge readings indicate? The system is undercharged. The system is overcharged. The system is normal. The evaporator pressure regulator is bad.
This system is normal
While testing a compressor clutch, a fused jumper wire is used to apply voltage directly from the battery to the clutch coil connector. This does not cause the compressor clutch to engage. The LEAST LIKELY cause of this is: an open compressor clutch coil. a shorted compressor clutch coil. an open compressor clutch circuit ground. an open clutch coil feed circuit.
an open clutch coil feed circuit (the jumper wire replaces the coil feed and getting no results shows that the problem is not for this compressor clutch)
To charge an A/C system while it is running, the refrigerant should be added to: the high side. the low side. both the high and low sides. either the high or the low side
the low side (On/Low, Off/High)