FREE Air Conditioning Repair System Diagnosis and Troubleshooting Questions and Answers

Question 1

A technician measures a very low superheat and an abnormally high subcooling on an air conditioning system that uses a thermostatic expansion valve (TXV).
Which of the following is the most likely cause of these readings?

Accepted Answer

Refrigerant overcharge

Answer

Inefficient compressor

Answer

Severe airflow restriction over the evaporator

Answer

Refrigerant undercharge

Question 2

A technician arrives at a service call to find the indoor evaporator coil is a solid block of ice. After properly and safely thawing the coil, which of the following should be the technician's FIRST diagnostic step?

Accepted Answer

Inspect the air filter and verify indoor airflow.

Answer

Check the refrigerant charge.

Answer

Measure the compressor amperage draw.

Answer

Replace the thermostatic expansion valve.

Question 3

A technician uses a multimeter to check the windings of a single-phase compressor motor. The readings are: Common to Run = 2 ohms, Common to Start = 6 ohms, and Run to Start = 8 ohms. A reading from any winding to the compressor casing shows infinity (OL). What do these readings indicate?

Accepted Answer

The motor windings are electrically sound.

Answer

A shorted winding.

Answer

An open winding.

Answer

The motor is shorted to ground.

Question 4

Which of the following is the most direct and primary indicator of non-condensables being present in a refrigeration system?

Accepted Answer

Excessively high discharge (head) pressure.

Answer

Unusually low liquid line temperature.

Answer

A completely frosted suction line.

Answer

Compressor failing to start.

Question 5

While diagnosing a system, a technician observes low suction pressure, low superheat, and a frosted evaporator coil only near its inlet. Further inspection reveals an abnormally high subcooling reading. What is the most probable diagnosis?

Accepted Answer

A restriction in the liquid line filter-drier.

Answer

A failed indoor blower motor.

Answer

A severe refrigerant undercharge.

Answer

An overcharged system.

Question 6

A technician uses a manometer to measure the total external static pressure (TESP) of an air handler and finds it to be 1.2 inches of water column (in. w.c.). The unit's data plate specifies a maximum TESP of 0.5 in. w.c. What does this high reading indicate?

Accepted Answer

There is excessive resistance to airflow in the duct system.

Answer

The blower motor is running too slowly.

Answer

There is significant leakage in the supply ductwork.

Answer

The return air filter is clean and the ductwork is oversized.

A technician measures a very low superheat and an abnormally high subcooling on an air conditioning system that uses a thermostatic expansion valve (TXV).Which of the following is the most likely cause of these readings?

A technician measures a very low superheat and an abnormally high subcooling on an air conditioning system that uses a thermostatic expansion valve (TXV).
Which of the following is the most likely cause of these readings?