FREE Refrigeration System Repair Question and Answers

Question 1

The cause of sporadic AC cooling is being identified. Both the high side and low side pressure gauge readings are displayed intermittently on the gauge set, and the high side occasionally decreases below 100 psi. What is the MOST likely reason for the following?

Accepted Answer

Stuck expansion valve

Answer

An intermittently stuck expansion valve is the most likely cause of sporadic AC cooling and fluctuating pressure readings. If the valve occasionally restricts flow too much or too little, it will lead to inconsistent refrigerant metering. When it restricts flow excessively, the high-side pressure might drop significantly (below 100 psi) as the compressor struggles to move refrigerant past the blockage, leading to inconsistent cooling.

Question 2

What happens in an evaporator in a cooling and refrigeration system?

Accepted Answer

The refrigerant absorbs the latent heat

Answer

In an evaporator, the low-pressure liquid refrigerant absorbs latent heat from the surrounding air, typically the cabin air in an AC system. As it absorbs this heat, the refrigerant changes phase from a liquid to a gas, effectively cooling the air that passes over the evaporator coil. This phase change and heat absorption are fundamental to the cooling process.

Question 3

The following statements about a receiver/dryer are all true, EXCEPT:

Accepted Answer

Evacuating system removes moisture from a saturated receiver/dryer

Answer

The question asks for the statement that is NOT true. While evacuating an AC system removes air and some moisture, it cannot remove moisture from a *saturated* receiver/dryer. Once the desiccant in the receiver/dryer is saturated with moisture, it loses its ability to absorb more and must be replaced, as evacuation alone cannot restore its function. The other statements correctly describe aspects of receiver/dryers.

Question 4

What happens in a condenser in a cooling and refrigeration system?

Accepted Answer

The refrigerant releases the latent heat.

Answer

In a condenser, the high-pressure, high-temperature gaseous refrigerant releases its latent heat to the cooler ambient air, typically aided by a fan. As it releases this heat, the refrigerant changes phase from a gas back into a liquid. This process is essential for dissipating the heat absorbed from the cabin and completing the refrigeration cycle.

Question 5

According to technician A, a gasket or O-ring is used to seal the system at every air conditioning connection. According to Technician B, lubricating the O-ring with the appropriate refrigerant oil before replacing it would help prevent nicks and make installation easier. Who is correct?

Accepted Answer

Both Technician A and B

Answer

Technician A is correct because AC systems operate under high pressure and require hermetic seals to prevent refrigerant leaks, which are provided by gaskets and O-rings at every connection. Technician B is also correct; lubricating O-rings with the appropriate refrigerant oil before installation is standard practice to prevent damage like nicks or twisting during assembly, ensuring a proper and durable seal. Both practices are crucial for effective AC system repair and maintenance.

Air Conditioning Repair Practice Test

Air Conditioning Repair Practice Test

FREE Refrigeration System Repair Question and Answers