How to Troubleshoot Common Problems in Electric Furnaces

A man works on a furnace.
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  • Beginner
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What You'll Need
Clamp-on ammeter

You should troubleshoot your furnace as soon as you detect problems because faulty electric furnaces can be a fire hazard. Follow these steps to perform the troubleshooting.

Step 1 - Disconnect the Power

Turn the furnace off by flipping the power switch on the furnace or, safer still, by shutting off the furnace's main circuit breaker (located next to the furnace or in your home's main service panel). You should disconnect electric furnaces before you remove the door (also called control or access panel).

Step 2 - Examine the Wires

Check for burnt or loose wires and parts to make sure that the problem is not simply one of wiring. Locate the thermostat wires in the furnace. Electric furnaces typically have white, yellow, green, and red wires. Test each wire with a clamp-on ammeter to see whether they are drawing current. Replace any defective wires.

Step 3 - Examine the Thermostat

Check the thermostat itself. It must be set higher than the actual room temperature. Check that there are fresh batteries.

Step 4 - Examine Breakers and Fuses

Check for flipped-off breakers and blown fuses in the fuse or circuit breaker panel. You can identify blown fuses when the wire filament inside the glass top cylinder is scorched. If you find defective fuses, replace them with new ones.

Step 5 - Examine Relay and Sequencer Coils

Check the relay and sequencer coils for resistance. Coils need servicing or replacing if your meter fails to read a measurable resistance. (In that case, you would need a professional to perform the repair.)

No Heat

For electric furnaces with no heat at all, you should ensure that the furnace switch or main breaker is properly closed. Check thermostat settings and replace the battery if necessary.

Insufficient Heat

For electric furnaces which put out insufficient heat, check the thermostat setting and battery. Try raising the thermostat setting. Check the fuse or breaker. Replace the fuse or flip on the breaker. Check the filter. If the filter is clogged, remove dust or replace the part.

Heat Cycles On and Off Too Often

For electric furnaces that cycle on and off too often, you should check the filter. If the filter is clogged, replace it. Otherwise oil and adjust the blower.

If none of these tips help, seek professional assistance.