Furnace Not Working? Try These DIY Heating Repair Tips

A surprising number of apparent furnace malfunctions occur because the homeowner hasn’t set the thermostat to “heat.” Double-check your thermostat settings and make sure it’s set to “heat” with the fan set to “auto” or “on.” If it still won’t kick on, raise the temperature five degrees. Make sure your heating registers are open and check your HVAC filter — a dirty HVAC filter can reduce efficiency and keep your furnace from working properly. 

If your HVAC filter is visibly dirty, you should change it now. If you haven’t changed it in the past six months, change it anyway, even if your furnace kicks on. HVAC filters should be changed every one to six months. Change them more often if you have pets or someone in your home has allergies, asthma, or other respiratory issues. Change them less often if you are pet-free and no one in your household has any breathing problems.

If your furnace won’t kick on at all, check the circuit breaker before you call a service professional. A furnace that won’t turn on is often the result of problems with the thermostat, or in the case of a gas furnace, an extinguished pilot light. However, a blown fuse or tripped circuit can also be the problem, and that’s a heater repair that’s easy enough to make on your own. Replace the fuse and reset the tripped breaker, then see if your furnace kicks on. 

If you have a gas furnace, it probably uses a pilot light to ignite the gas burner. If your furnace isn’t heating or won’t come on, you should check to make sure the pilot light is burning.

If you’re lucky, performing your DIY heater repair will be a simple matter of relighting the pilot light. There should be instructions on your furnace to help you. Most newer units are going to have an electric igniter for the pilot, which makes relighting it super easy.

To relight your pilot light, turn the gas valve off and leave it that way for five minutes in order for any residual gas in the air to disperse. When you’re ready to proceed, turn the gas valve to the pilot position. There should be a red button that you can press to prompt the flow of gas from the pilot burner. Press this button and hold it down for 30 to 60 seconds, while using a long match or barbecue lighter to light the gas coming out of the pilot burner. Keep holding the button down for the full 30 to 60 seconds after the pilot light is burning again, so that the thermocouple can warm up and start generating voltage.

If your pilot light won’t stay lit, you can try adjusting the flame adjustment screw, if your pilot light has one. Follow the manufacturer’s instructions for making this adjustment to your unit. If nothing you try gets the pilot light to stay lit, you need to call a professional — you probably need a new thermocouple. 

If you have an electric-ignition furnace, you may need to reset the ignition control module. This is the equivalent of re-lighting the pilot light. It’s as simple as turning off power to the furnace at the circuit breaker, and then turning it back on again. Listen for the spark of your furnace igniting and check for the glow of the hot surface igniter. If your furnace kicks off again right away, or doesn’t get hot enough to start heating, then you most likely need to clean the flame sensor.