ASE Practice Test (A7: Heating & Air Conditioning) 1 — Questions and Answers

Question 1: 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?

Bad pressure cycling switch
Low refrigerant
Locked-up compressor
Incorrect air gap (Correct answer)

Correct answer: Incorrect air gap

If the compressor clutch coil receives good power and ground but doesn't engage, the electrical circuit is functional, indicating a mechanical issue. The most likely mechanical problem is an incorrect air gap between the clutch pulley and the clutch plate. If this gap is too wide, the magnetic force generated by the coil is insufficient to pull the clutch plate into contact with the pulley, preventing engagement.

Question 2: An unknown refrigerant is discovered prior to recovery. The technician should be able to:

recover it and recycle it as R-12
recover it and recycle it as R-134a
discharge it into the atmosphere
recover it and treat it as contaminated (Correct answer)

Correct answer: recover it and treat it as contaminated

It is illegal and environmentally irresponsible to discharge any refrigerant into the atmosphere. When an unknown refrigerant is encountered, it cannot be safely recycled as a known type (like R-12 or R-134a) due to the risk of contamination and equipment damage. Therefore, the correct procedure is to recover the unknown refrigerant into a dedicated tank and treat it as contaminated for specialized disposal or reclamation.

Question 3: The following statements about air conditioning performance test are true, EXCEPT:

Obstructions of the cabin filter might create insufficient air circulation
Road debris might clog the condenser fins which lead to a decrease in performance
If the passenger side floor is wet, it could be a clogged evaporator drain line.
To avoid evaporator odor, you want to operate the AC in RECIRC instead of FRESH (Correct answer)

Correct answer: To avoid evaporator odor, you want to operate the AC in RECIRC instead of FRESH

Operating the A/C in RECIRC mode continuously can trap moisture and odors within the cabin and on the evaporator, promoting mold and mildew growth. To help prevent evaporator odor, it's often recommended to periodically use FRESH air mode, especially before turning off the vehicle, to dry out the evaporator and introduce fresh air. Therefore, the statement that RECIRC avoids odor is incorrect.

Question 4: 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?

A normal condition.
A low refriderant charge.
A faulty compressore clutch relay.
A missing fan shroud. (Correct answer)

Correct answer: A missing fan shroud.

At low speeds or stop lights, the engine's cooling fan and its shroud are crucial for drawing air through the condenser to dissipate heat. A missing fan shroud significantly reduces the fan's efficiency by allowing air to bypass the condenser. This leads to high-side pressure buildup and reduced A/C performance at low speeds, while sufficient natural airflow at highway speeds allows the system to cool effectively.

Question 5: If the condenser fan wasn't working, what high- and low-side pressure gauge values would a technician find?

High-side low and low-side high
Both high-side high and low-side are high (Correct answer)
High-side high and low-side low
Both high-side high and low-side are low

Correct answer: Both high-side high and low-side are high

If the condenser fan is not working, the condenser cannot effectively dissipate heat from the refrigerant. This causes the high-side pressure to become excessively high as the hot refrigerant gas cannot cool and condense. This high pressure then backs up through the system, leading to an abnormally high low-side pressure as well, as the system struggles to cycle the refrigerant.

Question 6: 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?

A bad pressure cycling switch
An incorrect air gap (Correct answer)
A seized compressor
A low refrigerant level

Correct answer: An incorrect air gap

When the compressor clutch coil has good power (14.2V) and ground, it indicates that the electrical circuit to the coil is functioning correctly. Therefore, the issue preventing clutch engagement is mechanical. An incorrect air gap between the clutch pulley and the clutch plate is the most likely mechanical cause, as a gap that is too wide will prevent the electromagnetic force from pulling the clutch plate into engagement.

Question 7: 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?

Both technicians (Correct answer)
Neither technician
Technician X
Technician Y

Correct answer: Both technicians

Technician X is correct: restricted condenser airflow prevents proper heat dissipation, causing high pressures on both the high and low sides of the A/C system. Technician Y is also correct: abnormally low pressures on both the high and low sides are a classic indication of an insufficient refrigerant charge, meaning there isn't enough refrigerant to properly circulate and build pressure.

Question 8: 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?

Both technicians
Neither technician
Technician X (Correct answer)
Technician Y

Correct answer: Technician X

Technician X is correct; a frozen spot on an A/C component or connection, like the condenser, typically indicates a restriction in the system. This restriction causes a sudden pressure drop and corresponding temperature drop at that point, leading to ice formation. Technician Y is incorrect; an overcharge of refrigerant would generally lead to excessively high pressures throughout the system, not a localized frozen spot.

Question 9: Which of the following factors is most likely to cause a car to overheat?

Clogged radiator (Correct answer)
Electric cooling fan runs all the time
Restricted heater core
Thermostat stuck open

Correct answer: Clogged radiator

The radiator's primary function is to transfer heat from the engine's coolant to the ambient air. A clogged radiator, whether internally by deposits or externally by debris blocking its fins, severely impedes this heat exchange process. This reduction in cooling efficiency causes the engine coolant temperature to rise excessively, leading directly to engine overheating.

Question 10: 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?

Both X and Y
Neither X nor Y
X only (Correct answer)
Y only

Correct answer: X only

Technician X is correct: evacuating an A/C system uses a vacuum pump to remove air and moisture (as water vapor) from the system. This is crucial to prevent corrosion and ensure efficient cooling. Technician Y is incorrect; evacuation removes gases and vapors but does not remove solid dirt particles; flushing or component replacement is needed for that.

Question 11: What is the approximate measurement of the A/C compressor high-pressure that release valve discharges refrigerant?

375 psi (2,585 kPa)
475 psi (3,275 kPa) (Correct answer)
200 psi (1,379 kPa)
325 psi (2,240 kPa)

Correct answer: 475 psi (3,275 kPa)

A/C compressor high-pressure release valves are safety devices designed to prevent system damage by discharging refrigerant if pressure becomes dangerously high. For most automotive R-134a systems, this relief pressure is typically set around 450-500 psi. A measurement of 475 psi falls within this common range, indicating the point at which the system is designed to vent to prevent catastrophic failure.

Question 12: 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?

Both technicians (Correct answer)
Neither technician
Technician X
Technician Y

Correct answer: Both technicians

Electric cooling fans offer precise control over refrigerant and engine coolant temperatures because they are directly managed by the vehicle's control module. This module utilizes various temperature and pressure sensors to adjust fan speed, allowing for more accurate and efficient thermal regulation than traditional belt-driven fans. Therefore, both technicians are correct in their understanding of electric fan operation and control.

Question 13: 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?

Both X and Y
Neither X nor Y
X only (Correct answer)
Y only

Correct answer: X only

A misadjusted temperature door, also known as a blend door, directly controls the mix of hot and cold air entering the cabin. If it's stuck or mispositioned towards the cold air side, it will prevent adequate heat from reaching the cabin, causing a poor heat complaint. A defective resistor trio, however, typically affects the lower blower motor speeds, not the high speed, which often bypasses the resistor.

Question 14: The refrigerant should be added to the following to charge an A/C system while it is running:

the low side only (Correct answer)
both the high and the low sides
either the high or the low side
the high side only

Correct answer: the low side only

When charging an A/C system while it is running, refrigerant must always be added to the low-pressure side. This ensures that the refrigerant enters the compressor as a vapor, preventing liquid slugging which can cause severe damage to the compressor. Adding liquid refrigerant to the high side or when the system is off can be dangerous and damaging.

Question 15: All of these statements regarding A/C-heater control panel service are true, except:

The negative battery cable needs to be disconnected before A/C control panel removal.
In an air-bag equipped vehicle, you must wait the specified period once the negative battery cable is disconnected.
You must discharge the refrigeration system before the A/C control panel removal. (Correct answer)
Self-diagnostic tests might indicate a defective A/C control panel in the computer-controlled system.

Correct answer: You must discharge the refrigeration system before the A/C control panel removal.

The A/C control panel is an electrical component located in the vehicle's dashboard and is not physically connected to the refrigerant lines of the air conditioning system. Therefore, discharging the refrigeration system is completely unnecessary when removing or servicing the control panel. Disconnecting the battery and waiting for airbag systems to de-energize are crucial safety steps for electrical work in the dash, and self-diagnostics can indeed identify control panel issues.

Question 16: 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:

A weak compressor.
A faulty control valve.
A faulty low pressure switch. (Correct answer)
A low refrigerant charge.

Correct answer: A faulty low pressure switch.

A variable displacement compressor adjusts its output based on demand. If it performs poorly in high-demand scenarios, it suggests insufficient cooling capacity. A weak compressor, a faulty control valve (which regulates displacement), or a low refrigerant charge would all directly lead to reduced cooling. A faulty low-pressure switch, however, typically prevents the compressor from engaging at all to protect the system, rather than causing poor performance during operation.

Question 17: 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?

Both X and Y
Neither X nor Y
X only
Y only (Correct answer)

Correct answer: Y only

If the heater blows only cold air despite the engine being at operating temperature, it indicates that hot coolant is not circulating through the heater core. A common cause for this is a low coolant level in the cooling system, which can create air pockets that prevent coolant flow to the heater core. A stuck-closed thermostat would prevent the engine from reaching operating temperature in the first place, which contradicts the problem description.

Question 18: 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?

Broken compressor reed valves
Normal operation
Low refrigerant level (Correct answer)
A restriction in the high side

Correct answer: Low refrigerant level

Low pressure (5 psi) on the low side and relatively low pressure (105 psi) on the high side, especially at an ambient temperature of 85°F, are classic symptoms of a low refrigerant charge. A properly charged system at this temperature would typically show higher pressures on both sides (e.g., 30-45 psi low, 180-250 psi high). Insufficient refrigerant means less heat transfer, resulting in reduced pressures throughout the system.

Question 19: With the temperature selector in the cool position, incoming air is heated in the vent position. What could be the issue?

Air blend door is stuck. (Correct answer)
Low coolant in the radiator.
Heater core is clogged.
Cooling fan is inoperative

Correct answer: Air blend door is stuck.

The air blend door, also known as the temperature door, controls the mixture of hot air from the heater core and cold air from the evaporator. If the temperature selector is set to cool but the incoming air is heated, it means the blend door is stuck in a position that allows hot air to enter the cabin, overriding the desired cool setting. Other options relate to cooling system issues or a clogged heater core, which would not cause heated air when cool is selected.

Question 20: 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?

Both technicians
Neither technician
Technician X (Correct answer)
Technician Y

Correct answer: Technician X

The compressor clutch relay acts as a protective switch, allowing a low-current signal from the control head to activate the higher-current circuit required to engage the compressor clutch. This prevents high amperage from damaging the sensitive control head. An open clutch relay winding would interrupt the circuit, preventing the clutch from engaging at all, not causing it to engage continuously.

Question 21: At an operating temperature, if a cooling system operates at too cool . Which of the following will the engine do?

Have less efficiency
Have more torque
Produce higher emissions (Correct answer)
Have ignition detonate

Correct answer: Produce higher emissions

An engine operating below its optimal temperature range (too cool) will experience less efficient combustion. This often leads to incomplete burning of fuel, resulting in an increase in harmful exhaust emissions such as hydrocarbons (HC) and carbon monoxide (CO). Modern engines are precisely calibrated to operate at specific temperatures for peak efficiency and emissions control.

Question 22: 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?

Both X and Y (Correct answer)
Neither X nor Y
X only
Y only

Correct answer: Both X and Y

If 14.2 volts are measured at the A/C clutch coil but it fails to engage, it indicates that power is present, but the circuit is not completing to create the magnetic field. This can be caused by an internal break in the clutch coil itself (a failed coil) or by an interruption in the ground path, preventing current flow through the coil. Both scenarios would result in voltage at the coil but no operation.

Question 23: 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?

Both technicians
Neither technician
Technician X (Correct answer)
Technician Y

Correct answer: Technician X

During normal operation, the A/C compressor compresses low-pressure, low-temperature refrigerant vapor into high-pressure, high-temperature vapor. This compression process inherently generates significant heat, making the compressor outlet (discharge line) very hot. This is a normal and expected part of the refrigeration cycle, indicating the compressor is doing its job.

Question 24: The following statements are true about an air conditioner's evaporator, EXCEPT:

The refrigerant changes from a vapor to a liquid as it receives heat from the cabin air. (Correct answer)
Refrigerant flows from the bottom to the top.
Refrigerant enters the evaporator as a liquid.
It removes humidity from the air.

Correct answer: The refrigerant changes from a vapor to a liquid as it receives heat from the cabin air.

In an air conditioner's evaporator, the refrigerant absorbs heat from the cabin air, causing it to undergo a phase change from a low-pressure liquid to a low-pressure vapor. The statement incorrectly describes this as changing from a vapor to a liquid. This phase change from liquid to vapor is the fundamental process that cools the air and removes humidity.

Question 25: Which of the following issues will result in the manifold gauge readings shown in the illustration?

Restricted condenser airflow
Refrigerant overcharge (Correct answer)
Low refrigerant
Expansion valve stuck closed

Correct answer: Refrigerant overcharge

An overcharge of refrigerant in an A/C system leads to excessively high pressures on both the high and low sides. The compressor works harder to compress the excess refrigerant, and the condenser struggles to dissipate the heat, resulting in elevated pressure readings throughout the system. The illustration would show abnormally high readings on both manifold gauges.

Question 26: The high side pressure in an A/C system exceeds the specifications. Any of these could be the cause, EXCEPT:

a plugged expansion valve
a broken compressor reed valve (Correct answer)
an overcharge of refrigerant
a restricted air flow across the condenser

Correct answer: a broken compressor reed valve

A broken compressor reed valve typically results in reduced compression efficiency. This would lead to lower-than-normal high-side pressure and higher-than-normal low-side pressure, or even equalization of pressures, as the compressor cannot effectively move refrigerant. It would not cause the high-side pressure to exceed specifications; instead, it would cause a loss of cooling performance due to insufficient pressure differential.

Question 27: When replacing the AC compressor, all of these tasks occur. Except:

Reuse existing compressor oil (Correct answer)
Reuse all mounting brackets
Use an equivalent or the same compressor
Installing new seals and gaskets

Correct answer: Reuse existing compressor oil

When replacing an A/C compressor, it is essential to drain the old refrigerant oil from the system and add the correct type and amount of new, clean refrigerant oil. Reusing existing compressor oil is incorrect because it may be contaminated, degraded, or its exact quantity unknown, which can lead to premature failure of the new compressor. The other listed tasks are standard and necessary for a proper compressor replacement.

Question 28: 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?

Both technicians
Neither technician
Technician X
Technician Y (Correct answer)

Correct answer: Technician Y

A blower motor resistor is responsible for creating different fan speeds by introducing varying amounts of resistance into the motor's circuit. If the resistor fails, it often breaks the circuits for the lower and medium speeds, leaving only the high-speed setting operational, as high speed typically bypasses the resistor entirely. A short in the power feed would likely blow a fuse or prevent the motor from working at all.

Question 29: 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?

Both X and Y
Neither X nor Y
X only (Correct answer)
Y only

Correct answer: X only

A compressor thermal protector is a safety device designed to open the compressor clutch circuit if the compressor overheats, preventing damage. If this protector fails in an open state, it will prevent the clutch from engaging, regardless of other system conditions. An incorrectly adjusted temperature door, however, controls cabin air temperature and does not directly affect the compressor clutch operation in a manual A/C system.

Question 30: The maximum capacity you can fill an A/C system recovery container with recovered refrigerant is:

80%
70%
60% (Correct answer)
50%

Correct answer: 60%

A/C system recovery containers must not be filled beyond 60% of their total capacity by weight. This safety regulation ensures that there is sufficient vapor space above the liquid refrigerant to accommodate thermal expansion. Overfilling can lead to dangerous over-pressurization of the tank, especially with temperature fluctuations, posing a significant safety risk.

ASE Practice Test (A7: Heating & Air Conditioning) 1

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?