Free Refrigeration System Repair Question and Answers — Questions 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?
- Stuck expansion valve (Correct answer)
- Overcharged A/C System
- Compressor internal leak
- Damaged compressor reed valve
Correct answer: Stuck expansion valve
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?
- The refrigerant evaporates latent heat.
- Latent heat is condensed
- Latent heat is released.
- The refrigerant absorbs the latent heat (Correct answer)
Correct answer: The refrigerant absorbs the latent heat
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:
- Evacuating system removes moisture from a saturated receiver/dryer (Correct answer)
- Clogged filter can cause higher than normal pressure
- Saturated desiccant can cause a blockage due to freezing
- You install a new desiccant bag on some systems before charging the system.
Correct answer: Evacuating system removes moisture from a saturated receiver/dryer
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?
- The refrigerant releases the latent heat. (Correct answer)
- Latent heat is increased
- The refrigerant absorbs the latent heat.
- Latent heat is pressurized.
Correct answer: The refrigerant releases the latent heat.
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?
- Technician B only
- Technician A only
- Neither Technician A nor B
- Both Technician A and B (Correct answer)
Correct answer: Both Technician A and B
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.
Question 6: Which of the following doesn't fit the definition of a compressor?
- Rotary
- Lateral (Correct answer)
- Screw
- Reciprocating
Correct answer: Lateral
The question asks which term does not fit the definition of a compressor type. Rotary, screw, and reciprocating are all recognized and common types of compressors used in various applications, including air conditioning systems. 'Lateral' is not a classification or type of compressor mechanism.
Question 7: The term EXCEPT appears in this query. Find the response to this question that CANNOT result in the specified circumstance. Before selecting an answer, thoroughly read the entire question. Regarding the expansion valve, EVERYTHING IS TRUE, EXCEPT FOR
- It can fail in the open position as a result of debris in the system.
- With moisture in the system, ice can form and cause blockage
- When stuck closed, pressure on high side is low and pressure on low side is high. (Correct answer)
- It can seize in the closed position due to a lack of lubricant.
Correct answer: When stuck closed, pressure on high side is low and pressure on low side is high.
The question asks for the statement that is NOT true regarding an expansion valve. If an expansion valve is stuck closed, it severely restricts refrigerant flow, causing the high-side pressure to become *very high* (as the compressor pushes against a blockage) and the low-side pressure to become *very low* (due to insufficient refrigerant reaching the evaporator). Therefore, the statement that high-side pressure is low and low-side pressure is high is incorrect.
Free Refrigeration System Repair Question and Answers
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?