Problem: My gas furnace will not turn on? Nothing happens when I turn the heat up on my thermostat to start my furnace. What could be the reason that my gas furnace will not start?
Answer: We have this question and problem asked many times. I have had this problem with my own furnace over the years. Below we have a great YouTube video made by AC Service Tech LLC that explains 8 reasons why that a gas furnace will not turn on. Many thanks to AC Service Tech for making this excellent troubleshooting video! Here are the 8 short reasons why the gas furnace will not turn on. If you would like an explanation of the reasons I would highly recommend watching this 12-minute video.
Reasons why a gas furnace will not turn on:
- No power to the furnace. Make sure that you check the power switch, the circuit breaker, and the door safety switch to make sure they are all on. You can tape the door safety switch down so the furnace will be on and check with a voltmeter set to “Volts AC” to see if you are getting power between L1 and neutral wire on the control board. You should be getting between 110 to 125 volts AC between L1 and neutral.
- You could have a bad transformer or a bad low voltage fuse. You should be getting 24 to 29 volts AC between the R and C terminals on the control board. We sell low voltage transformers on the following page: Please click here if you are interested in the low voltage transformers that we sell.
- Something could be opening the low voltage circuit like a condensate pump low voltage safety switch. Please click here if you are interested in the low voltage condensate pump safety switches we sell.
- The thermostat wire could be shorted out or you could have an intermittent electrical, loose connection.
- The thermostat could be bad. If your thermostat has batteries make sure the batteries are in good condition.
- The control board could be bad and the board might not be allowing power to go to the inducer motor. You could have a bad relay on the control board. Please click here if you are interested in the furnace control boards that we sell.
- The inducer motor might have a bad inducer motor capacitor. Please click here if you are interested in the inducer motor capacitors that we sell.
- The inducer motor might be bad. You might need a new draft inducer. Please click here if you are interested in the draft inducers that we sell.
Below is a great video made by AC Service Tech that explains the 8 reasons why a gas furnace does not start. Thanks so very much AC Service Tech!
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