FREE Air Conditioning Repair Electrical Systems and Controls Questions and Answers

Question 1

A technician measures the voltage to the coil of a contactor in a residential condensing unit and reads 0 volts, even though the thermostat is calling for cooling.
Which of the following is the most likely cause?

Accepted Answer

The high-pressure safety switch is open.

Answer

The contactor coil is shorted.

Answer

The dual-run capacitor has failed.

Answer

The line voltage at the disconnect is too low.

Question 2

When testing a dual-run capacitor with a multimeter, a technician should measure the microfarad (µF) reading between which terminals to check the capacitance for the compressor motor?

Accepted Answer

Between the 'C' (Common) and 'HERM' (Hermetic) terminals.

Answer

Between the 'C' (Common) and 'FAN' terminals.

Answer

Across the 'HERM' and 'FAN' terminals.

Answer

Across any two of the three terminals.

Question 3

What is the primary function of a sequencer in an electric furnace with multiple heating elements?

Accepted Answer

To stage the activation of heating elements and the blower.

Answer

To regulate the control circuit voltage to 24V.

Answer

To act as a safety limit switch in case of overheating.

Answer

To control the speed of the indoor blower motor.

Question 4

A technician is troubleshooting a condenser fan motor that is not running. The wiring diagram shows a black wire connected to the contactor, a brown wire to the 'FAN' terminal of the capacitor, and a white wire to the 'C' terminal. Which wire provides the start winding with the necessary phase shift from the capacitor?

Accepted Answer

The brown wire

Answer

The black wire

Answer

The white wire

Answer

The ground wire

Question 5

Which of the following components is responsible for stepping down line voltage to provide the 24V AC used by the thermostat and control circuits in most residential HVAC systems?

Accepted Answer

A transformer

Answer

A relay

Answer

A capacitor

Answer

A contactor

Question 6

A customer reports a loud buzzing or chattering noise from their outdoor unit when the air conditioner tries to start. Which electrical component is the most likely source of this noise?

Accepted Answer

The contactor

Answer

The dual-run capacitor

Answer

The low-pressure switch

Answer

The crankcase heater

A technician measures the voltage to the coil of a contactor in a residential condensing unit and reads 0 volts, even though the thermostat is calling for cooling.Which of the following is the most likely cause?

A technician measures the voltage to the coil of a contactor in a residential condensing unit and reads 0 volts, even though the thermostat is calling for cooling.
Which of the following is the most likely cause?