Air Conditioning Repair Car Air Conditioning Repair 3

Question 1

Which refrigerant replaced R-12 in most automotive AC systems manufactured after 1994?

Accepted Answer

R-134a

Answer

R-134a became the standard automotive refrigerant after the EPA phased out ozone-depleting R-12 under the Clean Air Act, though newer vehicles use R-1234yf.

Question 2

A customer complains of a musty odor from the AC vents but normal cooling. What is the most likely cause?

Accepted Answer

Mold or bacteria growth on the evaporator coil

Answer

Moisture and organic debris on the evaporator surface create an ideal environment for mold and bacteria, producing a musty smell that enters the cabin through the vents.

Question 3

What does TXV stand for in an automotive AC system, and what is its function?

Accepted Answer

Thermal Expansion Valve — meters refrigerant flow into the evaporator

Answer

The Thermal Expansion Valve (TXV) regulates the amount of refrigerant entering the evaporator based on evaporator outlet temperature, optimizing efficiency.

Question 4

Both high-side and low-side pressures are abnormally low on a running AC system. What does this most likely indicate?

Accepted Answer

System is undercharged (low refrigerant)

Answer

When both pressures are uniformly low, the refrigerant charge is insufficient to maintain normal operating pressures on either side of the system.

Question 5

When replacing an AC compressor, why must a specific amount of oil be added to the new unit?

Accepted Answer

To compensate for oil retained in old system components

Answer

Old system components (condenser, evaporator, lines) retain a portion of compressor oil, so the replacement compressor must be pre-filled to match total system oil capacity.

Air Conditioning Repair Practice Test

Air Conditioning Repair Practice Test

Air Conditioning Repair Car Air Conditioning Repair 3