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Gas furnace short cycling

Mappleman Member Posts: 2
I'm an oil heat guy.. A buddy of mine has a gas fired hot air furnace that is short cycling. It will satisfy the t-stat eventually, but it only stays lit for about three minutes before it shuts the burner off, relights, runs three min., then shuts off again. I've not looked at it yet, I'm looking for some place to start, (besides the flame roll out switch)


  • JStar
    JStar Member Posts: 2,752

    High limit safety. Take a temperature difference. The supply shouldn't be hotter than the max rating for the safety. Should be specified on the nameplate. A high delta T is a cause for concern.

    Flame sensor may be dirty or faulty.

    Pressure switch could be opening during the cycle.

    Gas valve, safety, or control wire terminals could be rusted or pitted.
  • Mappleman
    Mappleman Member Posts: 2
    Gas furnace short cycling

    Thanks for the start points, I'll be at it this weekend. (no free work during the week)
  • Tim McElwain
    Tim McElwain Member Posts: 4,593
    Send me an E-mail and

    I will send you a step by step checkout. My e-mail is [email protected]
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