ASE Practice Test (A7: Heating & Air Conditioning)

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?

Accepted Answer

Incorrect air gap

Answer

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:

Accepted Answer

recover it and treat it as contaminated

Answer

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:

Accepted Answer

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

Answer

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?

Accepted Answer

A missing fan shroud.

Answer

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?

Accepted Answer

Both high-side high and low-side are high

Answer

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.