FREE Air Conditioning Repair System Diagnosis and Troubleshooting Questions and Answers

Question 1

A technician connects gauges to an operating air conditioning system and observes that both the suction (low-side) and head (high-side) pressures are significantly lower than normal.
Which of the following is the most likely cause?

Accepted Answer

A low refrigerant charge

Answer

A dirty condenser coil

Answer

A severe refrigerant overcharge

Answer

Non-condensables in the system

Question 2

When diagnosing a system with a thermostatic expansion valve (TXV), a technician measures a high condenser subcooling and a normal to low superheat. What is the most likely diagnosis?

Accepted Answer

Refrigerant overcharge

Answer

Failed compressor valves

Answer

Low refrigerant charge

Answer

Restriction in the liquid line

Question 3

A technician is troubleshooting a compressor that hums for a few seconds and then trips the thermal overload. After safely disconnecting power and discharging the capacitor, a multimeter check shows the capacitor's microfarad (µF) reading is well below its rating. What is the most appropriate next step?

Accepted Answer

Replace the run capacitor.

Answer

Ohm out the compressor windings.

Answer

Add refrigerant to the system.

Answer

Replace the contactor.

Question 4

A customer with a heat pump complains that it is blowing warm air when the thermostat is set to 'cool'. A technician on-site confirms the outdoor unit is running, but the larger, insulated refrigerant line (the suction line) is hot. Which of the following is the most probable cause?

Accepted Answer

A reversing valve stuck in heat mode

Answer

A failed condenser fan motor

Answer

An undercharged system

Answer

A clogged filter-drier

Question 5

To accurately evaluate total system airflow and diagnose potential restrictions in ductwork, which of the following measurements is most essential?

Accepted Answer

Total external static pressure

Answer

Temperature drop across the evaporator coil

Answer

Velocity pressure in the return duct

Answer

Amperage draw of the indoor blower motor

Question 6

A technician uses a megohmmeter to test a compressor's windings to ground. The meter displays a reading of 0.5 MΩ (megohms). What does this result indicate?

Accepted Answer

The motor insulation is breaking down and shorted to ground.

Answer

The compressor windings are open.

Answer

The compressor's crankcase heater is working.

Answer

The compressor is acceptable for service.