Your furnace is the most essential appliance in your house, especially when the weather turns cold. Fortunately, you can usually fix a problem with your heater without the need to call in a professional.

Before troubleshooting, ensure your furnace’s electrical power switch is off. Then, remove the front access panel to better view the pilot light.

Check the Thermostat

Your furnace is one of the most essential appliances in your home, significantly as temperatures drop. Knowledge about troubleshooting common difficulties can help you rapidly restore heat to your house and save money on expert repairs.

Start your Furnace Repair and Troubleshooting by checking the thermostat. Ensure it is set to “heat” and is at least five degrees higher than room temperature. Also, ensure that the programmable settings are correct for date and time, as these can affect your heating process.

If your thermostat displays an error code on the screen, it could indicate it’s time to replace the batteries. It’s also worth opening up the cover to check that all wires are securely connected. You can also use a multimeter to verify that the breaker switch on the furnace is in the “On” position. If not, flip the switch over to the “On” position and try restarting your system. If you continue to experience trouble, you may have a dirty flame sensor or pilot assembly.

Check the Power

Ensure the power switch is on and the circuit breaker hasn’t tripped if your furnace won’t start. Switch the breaker back on, then try restarting the furnace.

Clean or replace your filter. A clogged filter restricts airflow, and increases wear on other furnace components.


Dirty flame sensor rod

The metal rod that confirms a burner flame is present during ignition can get coated with combustion soot and fail to turn the gas valve on. When this happens, your furnace will shut off for safety.

Take the access panel off and inspect the ignitors (they look like ceramic components with electrical connections on each end). If they are brown, yellow, or black, dust them off using canned air or a brush. Once clear, put the access panel back on and re-open the gas valve. Then, test the voltage from L1 to Neutral and from the loose Ground wire to the cabinet. They should read “0” volts.

Check the Pilot Light

When your gas furnace doesn’t start, it can be unpleasant, particularly in the winter. But before you panic and call in a professional, look at the pilot light. A properly functioning pilot light will glow blue with a hint of yellow at the top. You can check this by removing the small door on the bottom of the front cover and looking inside the burner chamber. You’ll also need to turn off the gas valve and wait for a few minutes so that any accumulated gas can dissipate.

Once you’ve done this, relight the pilot light using the procedures printed on the cover panel or your owner’s manual. If the pilot light is continually going out, there can be a problem with the thermocouple or the gas supply that has to be fixed by a professional. Luckily, this is usually easy to set and requires little time and effort. Then, you can get back to the comfort of your home.

Check the Fan

Many older furnaces used to have a pilot light, but newer systems ignite electrically instead. If yours fails to start or clicks and then shuts off, the problem may be a dirty sensor or ignitor. Shut off the power to your furnace, turn off the gas (consult your user’s manual for instructions), and remove the probe to inspect. If it looks cracked or damaged, replace it and restart your system.

It’s also possible your furnace’s power switch has been flipped to the “Off” position. It looks very similar to a light switch, and it’s easy for someone to accidentally flip it off when trying to fix something else in the house. Fortunately, you can reset it to resume heating. Lastly, you can check the exterior gas valve to see if it has been closed. This safety feature shuts the system down if it detects an unauthorized flame rolling out from the burner.


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