DIY Furnace Repair — How to Troubleshoot Heater Problems

January 18, 2017 Katie Hoffman

DIY Furnace Repair

Troubleshooting your heater problems may be easier than you think.


Before you begin troubleshooting your AC unit, here is one warning. Many times a homeowner attempts a repair, and then ends up causing a problem that is worse than the original issue. If you are not comfortable working on more complicated repairs, we are here to help. Also, if you get stuck or can’t find the part you need, we are happy to come … But if you are comfortable with… I hope this guide will


  1. The first two fixes are very simple, but can make a big difference. First, make sure that your filter is clean and not plugged. Change your filter if you have not done so in the last couple months. Most filters need to be changed once every 30 days, but some are made to be changed every 3 months.
  2. Next, double check that your thermostat is set to “heat.” It can be easy to forget to make this change.
  3. Third, check to make sure the furnace door is attached and sealed. If the door is opened, the furnace will not turn on.
  4. Fourth, go to your breaker panel and double check that the breaker that controls your HVAC system is in the ON position. (If your breaker is being tripped by the HVAC unit, it is a good idea to have a safety inspection done on your equipment.)
  5. At this point, you will definitely need to shut off the power at the unit and at the circuit breaker before doing any more serious troubleshooting.
  6. Sixth, using the service manual that came with your HVAC unit, find the ignitor, flame sensor, and limit switch. If you no longer have your original manual, a google search for “furnace diagram” should return some helpful pictures. Be sure that you find the correct picture for your specific unit, since many furnace and HVAC systems are different.
  7. With these locations in mind, each of these parts can be replaced. I would recommend watching several youtube videos before starting (to become familiar with the repairs). Also, order the parts you will need. Some parts are only available to licensed HVAC contractors, but other parts can be purchased at Harbor Freight or similar retailers.
  8. If the problem with your heater is from the fan motor or gas valve, these repairs should be done be someone who is familiar with this type of job and the sealants needed to prevent carbon monoxide from leaking into your home. A gas valve needs to be properly calibrated to prevent your heat exchanger from burning up.
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