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Problem My Gas Furnace will not turn On? Nothing Happens?

Troubleshooting Gas & Electric Furnaces

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:

  1. 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.
  2. 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.
  3. 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. 
  4. The thermostat wire could be shorted out or you could have an intermittent electrical, loose connection.
  5. The thermostat could be bad. If your thermostat has batteries make sure the batteries are in good condition.
  6. 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. 
  7. 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. 
  8. 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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2 thoughts on “Problem My Gas Furnace will not turn On? Nothing Happens?

  1. Why has my question about high limit switches on a York 80 circa 1999 not been answered?

    1. I answered your question on November 4th. Sorry that you did not get my answer. I copied my answer below:
      Hi Lawrence! I would like to suggest that you watch your furnace during a heating cycle. Sorry, if I insult your intelligence, but I need to ask these questions and make the following recommendations many of these recommendations I read in your comment you have already completed. I would ask the questions: Is your furnace gas shutting off and is your furnace going off on high limit? If it is then this is the reason that you are going through so many limit switches. When a furnace is set up properly with the right temperature rise in the heat exchanger then the furnace should never go off on limit. The limit as I am sure you know is a safety control that should only be used to shut the furnace off if your furnace over-heats like in that case that a blower motor failed. If your furnace is going off on limit I would suggest making sure that the blower motor capacitor is in good condition, make sure that your evaporator AC coil is not stopped up on the underside, make sure that your gas valve pressure is adjusted properly to produce the furnace recommended temperature rise. Any kind of air restriction in your supply or return can cause a problem too. Make sure all registers are open and unobstructed. I hope you can easily find and fix the problem. Steve

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