ASE Practice Test (A7: Heating & Air Conditioning)
Power and ground at the clutch coil are good, but the compressor clutch will not engage. Which of the following is the MOST LIKELY reason for the problem?
Correct answer: Incorrect air gap
With power and a ground, the clutch should have worked unless the gap is too wide, and is the most likely cause.
An unknown refrigerant is discovered prior to recovery. The technician should be able to:
Correct answer: recover it and treat it as contaminated
If an unknown refrigerant is identified, you have to recover it and treat it as contaminated.
The following statements about air conditioning performance test are true, EXCEPT:
Correct answer: To avoid evaporator odor, you want to operate the AC in RECIRC instead of FRESH
The opposite is actually true. If you want to avoid evaporator odor, you would want to set the system to FRESH mode instead. All of the other three options are correct.
At low speeds and stop lights, a vehicle's air conditioning performance is reduced, but it cools at highway speeds. Which of the following is the MOST LIKELY cause of this condition?
Correct answer: A missing fan shroud.
Most likely cause of the problem is a missing fan shroud.
If the condenser fan wasn't working, what high- and low-side pressure gauge values would a technician find?
Correct answer: Both high-side high and low-side are high
An inoperative condenser fan can cause a high high-side and high low-side reading. Answer option A is wrong because high high-side and low low-side pressure generally indicates a restriction evaporator air flow. B is wrong because high low-side and low high-side pressure indicate internal compressor damage. C is wrong because when both high and low-side pressure are low you can have the following faults: low charge, suction line obstruction, clogged orifice tube, stuck closed TXV valve and restricted line from the condenser to the evaporator.
The compressor clutch isn't going to engage. The technician discovers 14.2V and a good ground at the clutch coil connector during testing. Which of these possibly be the source of the problem?
Correct answer: An incorrect air gap
An incorrect air gap could be the cause of the problem.
Technician X states that when the condenser airflow is restricted, the pressure is high in both the high and low lines. Technician Y states that when both high and low sides show low pressure, it’s often an indication of low refrigerant. Who is correct?
Correct answer: Both technicians
Both of these techs have correct answers. When the pressure is high in both lines, it can indicate that the condenser airflow has been restricted. In addition, low pressure in both sides might indicate low refrigerant.
A frozen spot is noticed in the center of the condenser. Technician X says a frozen spot on a component or connection indicates a restriction in the system. Technician Y says this is caused Too much freon. Who is correct?
Correct answer: Technician X
Technician X is right. A frozen spot on a component or connection indicates a restriction in the system.
Which of the following factors is most likely to cause a car to overheat?
Correct answer: Clogged radiator
A clogged radiator is the most likely cause because a restriction of any kind in the cooling system will cause an engine to overheat. Answer option A is not a most likely cause because a constantly running cooling fan will not cause overheating. B is not a most likely cause because a restriction heater core will cause no heat but not necessarily cause an engine overheat. C is also wrong because a stuck open thermostat will not cause overheating.
Technician X says that evacuating an A/C system will remove air and moisture from the system. Technician Y says that evacuating an A/C system will remove dirt particles from the system. Who is right?
Correct answer: X only
Technician X is right. Evacuating an A/C system will remove air and moisture from the system.
What is the approximate measurement of the A/C compressor high-pressure that release valve discharges refrigerant?
Correct answer: 475 psi (3,275 kPa)
The high-pressure relief valve keeps the pressures from reaching points where the compressor begins to lock up. This could also lead to other damage because of the high pressures. This part discharges refrigerant at about 475 psi (3,275 kPa).
Two technicians are discussing electric cooling fans and air conditioning performance. Technician X says electric fans regulate refrigerant temperatures more precisely than belt driven fans do. Technician Y says electric cooling fans are controlled by control modules that use temperature and pressure actuated sensors and switches. Who is correct?
Correct answer: Both technicians
Both technicians are right.
Technician X says a misadjusted temperature door could cause a poor heat complaint. Technician Y says a defective resistor trio can cause a no high blower condition. Who is right?
Correct answer: X only
Technician X is right because a misadjusted blend door affects heat. Technician Y is wrong because the high blower is controlled by the high blower relay not the resistor trio.
The refrigerant should be added to the following to charge an A/C system while it is running:
Correct answer: the low side only
To charge an A/C system while it is running, the refrigerant should be added to the low side only.
All of these statements regarding A/C-heater control panel service are true, except:
Correct answer: You must discharge the refrigeration system before the A/C control panel removal.
Any time you test, inspect, replace or service the heating and A/C control panel assemblies, you must take certain steps. First, you’ll want to disconnect the negative battery cable. Then, you also need to wait a certain time before you begin working on the panel.
In high-demand scenarios, an air conditioning system with a variable displacement compressor performs poorly. ALL OF THESE ARE POSSIBLE CAUSES, WITH THE EXCEPTION OF:
Correct answer: A faulty low pressure switch.
A faulty low pressure switch could not be the cause of the problem.
The heater blows out only cold air at operating temperature. Technician X says a stuck closed thermostat could be the cause. Technician Y says the cooling system could be low on coolant. Who is right?
Correct answer: Y only
Technician Y is right because when the system is low on coolant there is insufficient material to transfer the heat. Technician X is wrong because a stuck thermostat causes overheating resulting in high temperatures and plenty of heat.
The low pressure gauge reads 5 psi and the high pressure gauge reads 105 psi with the A/C system operating at an ambient (outside) temperature of 85° F. What do these numbers imply?
Correct answer: Low refrigerant level
These readings indicate of a low refrigerant level.
With the temperature selector in the cool position, incoming air is heated in the vent position. What could be the issue?
Correct answer: Air blend door is stuck.
If the heater core was clogged, there would be no or little heat. If the cooling fan wasn’t working, the vehicle would overheat. It would also overheat with low coolant levels.
Technician X says the clutch relay protects the control head from the clutch circuit's high current. Technician Y says open clutch relay windings result in compressor clutch engagement at all times. Who is correct?
Correct answer: Technician X
Technician X is right. A clutch relay protects the control head from the clutch circuit's high current.
At an operating temperature, if a cooling system operates at too cool . Which of the following will the engine do?
Correct answer: Produce higher emissions
A specific engine temperature is needed to consume all of the pollutants.
The technician measures 14.2 volts at the A/C clutch coil, but the A/C clutch will not engage. Technician X says that a failed clutch coil could be the cause. Technician Y says that a failed clutch coil ground could be the cause. Who is right?
Correct answer: Both X and Y
Both technicians are right.
During a performance test, technicians notice the compressor outlet is hot. Technician X believes this is normal. Technician Y believes the system is overcharged. Who is correct?
Correct answer: Technician X
Tech X is correct; this is a normal occurrence. If the system had an overcharge, the compressor outlet would be cold, not hot. Because of this, there’s nothing unusual to be concerned about.
The following statements are true about an air conditioner's evaporator, EXCEPT:
Correct answer: The refrigerant changes from a vapor to a liquid as it receives heat from the cabin air.
Above statements are true, except that the refrigerant changes from a vapor to a liquid as it receives heat from the cabin air.
Which of the following issues will result in the manifold gauge readings shown in the illustration?
Correct answer: Refrigerant overcharge
When both the low and high sides are high, this indicates a refrigerant overcharge or restricted condenser. Courtesy of Toyota.
The high side pressure in an A/C system exceeds the specifications. Any of these could be the cause, EXCEPT:
Correct answer: a broken compressor reed valve
A broken compressor reed valve could be the cause of a high side pressure in an A/C system is above the specs.
When replacing the AC compressor, all of these tasks occur. Except:
Correct answer: Reuse existing compressor oil
When you replace the AC compressor, you should always install new seals and gaskets. You can use the same or an equivalent compressor and reuse the mounting brackets. What you don’t want to do is reuse the existing compressor oil.
A blower motor operates only in high speed. Technician X says there could be a short in the motor's power feed. Technician Y says it may have a faulty blower motor resistor. Who is correct?
Correct answer: Technician Y
Technician Y is correct. It may have a faulty blower motor resistor if a blower motor operates only in high speed.
On a manual air conditioning system without automatic control, the compressor clutch does not operate. Technician X says there is a failed compressor thermal protector. Technician Y says there is an incorrectly adjusted temperature door. Who is right?
Correct answer: X only
Technician X is correct because if thermal protector fails the B+ path to the compressor clutch is open and it is the most likely cause. Technician Y is wrong because temperature door position does not affect compressor operation on a manual system.
The maximum capacity you can fill an A/C system recovery container with recovered refrigerant is:
Correct answer: 60%
The only correct answer is 60%. All refrigerant storage containers need to be filled to 60% of the gross weight rating.
