FREE Air Conditioning Repair Compressor Diagnostics and Repair Questions and Answers

Question 1

A technician is diagnosing a residential split-system air conditioner.
The compressor runs but the suction line is very cold and frosting back to the compressor, while the discharge line is only slightly warm.
The high-side pressure is significantly lower than normal, and the low-side pressure is higher than normal.
What is the most likely issue with the compressor?

Accepted Answer

Worn or broken compressor valves (bad reeds)

Answer

Overcharged refrigerant system

Answer

Restriction in the liquid line filter-drier

Answer

Contaminated refrigerant leading to acid formation

Question 2

Which of the following diagnostic tools is most appropriate for precisely identifying an intermittent internal compressor short or ground fault without needing to open the refrigerant circuit?

Accepted Answer

Megohmmeter (insulation resistance tester)

Answer

Manifold gauge set

Answer

Clamp-on ammeter

Answer

Thermocouple psychrometer

Question 3

During a compressor replacement, after the new compressor is installed and the system is evacuated, what is a crucial step to ensure proper lubrication and prevent immediate failure, especially if the old compressor failed due to burnout?

Accepted Answer

Adding the correct type and amount of compressor oil

Answer

Pressurizing the system with nitrogen to check for leaks

Answer

Running the compressor in a vacuum for 15 minutes

Answer

Immediately adding the full refrigerant charge as a liquid

Question 4

A technician observes that a scroll compressor is making an unusually loud 'rumbling' or 'grinding' noise during operation. The system's pressures are somewhat off, but the compressor is still moving refrigerant. What is the most probable mechanical failure within the compressor?

Accepted Answer

Damaged or worn scroll plates

Answer

Excessive internal oil viscosity

Answer

Failed crankcase heater

Answer

Contaminated electrical contacts

Question 5

When performing a 'hard start kit' installation, which of the following components is primarily being addressed to improve compressor starting torque?

Accepted Answer

Run capacitor and start capacitor (combined in some kits)

Answer

Overload protector

Answer

Contactor coil

Answer

Crankcase heater

Question 6

A compressor repeatedly trips its internal thermal overload protector shortly after starting, even though the ambient temperature is moderate and the condenser coil is clean. System pressures appear normal before the trip. What is the most likely cause?

Accepted Answer

High compressor amperage due to internal motor winding issues

Answer

Undercharge of refrigerant causing the compressor to overheat

Answer

Low voltage supply to the outdoor unit

Answer

Restriction in the suction line