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Gas Furnace Cycling Off Repeatedly?

One of the most common issues in early winter, are Gas furnaces that wont stay running! They repeatedly cycle on and off, only heating for 2-5 minutes. This is commonly referred to as Short Cycling.

You may have a gas furnace thats several years old yourself. During a cold snap the furnace won't heat the house to desired temps. It will turn on, ignite and provide heat for a short period of time and then turn back off, after only a few short minutes of relief.

Many people jump right at replacing the thermostat, hoping it will fix the issue, but alas, its not likely the problem. You may see a flashing light which is a diagnostic code and may flash 3 or 4 times. You can refer to your user manual, which is usually left on top of the furnace, to diagnose these codes. Many short cycle issues are caused by something simple like a dirty flame sensor.

Short Cycling is caused by one main thing- your furnace overheating, and the safety mechanisms, automatically shutting it down. Regardless, it should be treated as a very serious problem as there have been cases of leaky heat exchangers causing this to occur as well.

One of the first things to check is that you have adequate airflow going to the unit. Check all your filters and make sure they are allowing air to pass through. If they are dirty, replace the filters and try the unit again. If this makes no difference, check to be sure hot air is not blowing directly onto your thermostat, causing the call for heat to be met soon after the unit turns on.

If all else fails, you are much better off calling out a service company to come and diagnose the problem for you. There are simply too many areas that need to be considered, for a homeowner to diagnose on their own. Always check with Angies List before calling a contractor. You will find unsolicited reviews from people just like yourself of the best contractors in your area, as well as the costs that people paid for the work.

If you know what is broken and want to attempt the repair on your own, take a look through our eBay store for the Furnace Replacement Parts at quite a discounted price!

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3 thoughts on “Gas Furnace Cycling Off Repeatedly?

  • February 28, 2010 at 2:24 pm

    After sitting for a while and all cooled down half of the time i turn on the heater the following occurs:

    When I turn on the heater from the brand new thermostat th heater fan comes on but the fire doesn’t ignite from the pilot light. Normally when it does ignite you can hear a whoosh sound but when this problem occurs it this sound doesn’t occur. I have three mechanics replace the circuit board in the furnace but the problem just starts up again when it wants to. When it is in this mode it will cycle on and off every couple of minutes but never ignite.

    The heater is at least 20 years old but the last mechanics said it was good heater (Trane) and is still in good shape.

    Thanks for your help!

  • May 17, 2011 at 11:25 am

    THANK YOU for this tip! Our furnace was doing exactly this. I went home, followed the procedure for a dirty flame sensor, and voila! Furnace is working properly again. You just saved me at least $150.

  • May 17, 2011 at 1:52 pm


    Glad we could help! Sometimes some simple troubleshooting can ease the problems quickly…

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