Air Conditioning Repair Electrical Systems and Controls 2

Question 1

A technician measures voltage across a contactor coil and reads 24V AC, but the contactor does not pull in. What is the most likely cause?

Accepted Answer

Open circuit in the coil winding

Answer

If 24V AC is present at the coil terminals but the contactor won't pull in, the coil winding itself is open and must be replaced.

Question 2

Which wire color is used for the common terminal in a standard 24V thermostat wiring system?

Accepted Answer

Blue or Black

Answer

The C (common) wire is typically blue or black, completing the 24V control circuit back to the transformer secondary.

Question 3

A single-phase 240V compressor motor draws significantly more current than its nameplate FLA rating. Which component failure would most likely cause this?

Accepted Answer

Failed run capacitor

Answer

A failed run capacitor reduces the motor's power factor and efficiency, causing it to draw excess current above its rated FLA.

Question 4

What does a locked rotor amperage (LRA) rating indicate on a compressor nameplate?

Accepted Answer

Current draw when the motor shaft is stationary

Answer

LRA is the inrush current drawn by the compressor motor at startup before the rotor begins to spin.

Question 5

An air handler blower motor runs continuously but does not respond to thermostat fan mode changes. Where should the technician first check?

Accepted Answer

Fan relay or control board fan output

Answer

If the blower ignores thermostat commands, the fan relay or control board output signal is likely stuck closed or shorted.

Air Conditioning Repair Practice Test

Air Conditioning Repair Practice Test

Air Conditioning Repair Electrical Systems and Controls 2