Question 1

When troubleshooting a residential air conditioning system, the technician reads 24 volts across the high-pressure control. What would be the most likely problem?

Accepted Answer

A dirty condenser can cause high pressure in the system, leading the high-pressure control to open and show 24 volts across it, indicating it is functioning correctly by cutting off the circuit.

Question 2

When troubleshooting a residential heating system, the technician reads 24 volts at the gas valve on a call for heat, but the gas valve does not energize. What would be the most likely problem?

Accepted Answer

The most likely problem is a defective gas valve. If the technician reads 24 volts at the gas valve during a call for heat, it indicates that the control circuit is functioning correctly up to that point, including the thermostat, transformer, and any low-voltage fuses. The presence of the correct voltage at the gas valve without it energizing suggests that the valve itself is faulty.

Question 3

List the four components that make up an electrical circuit.

Accepted Answer

The answer of List the four components that make up...

Question 4

When troubleshooting a residential heating system, the technician reads 24 volts across R and W on the furnace low-voltage terminal strip with the thermostat set to call for heating. What would be the most likely problem?

Accepted Answer

The 24 volts across R and W on the low-voltage terminal strip indicates that the thermostat is calling for heat and the signal is reaching the furnace. However, if the furnace is not responding, then the thermostat may be defective and not properly communicating with the furnace. The other options (defective gas valve, defective transformer, blown high-voltage fuse) would typically result in no voltage at all on the low-voltage terminal strip, rather than voltage being present but the furnace not responding.

Question 5

List four conclusions that can be made about a residential HVAC system when the fan switch is turned to "ON" and the fan motor starts.

Accepted Answer

The answer of List four conclusions that can be made...

Question 6

When troubleshooting a residential air conditioning system, the technician notices the condenser fan motor operating, but the compressor is not. What is the most likely cause?

Accepted Answer

If the condenser fan motor is operating but the compressor is not, it is likely due to a defective compressor, as the fan and compressor typically share the same power source and control circuit.

Quiz 22: Electrical Troubleshooting