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Diagnose a Furnace Pilot Light Problem

  • Transcript

    LESLIE: Betty in Minnesota, welcome to The Money Pit. How can we help you today?

    BETTY: Well, I sure hope you can because it’s really cold up here …

    TOM: OK.

    BETTY: … and my furnace is on the blink.


    TOM: What’s going on?

    BETTY: It won’t stay lit. It will keep running. I light it and it gets nice and warm and runs and the pilot light goes out but the motor keeps blowing cold air.

    TOM: Well, the way a furnace works is when the burners come on the furnace heats up and then, when it gets warm enough, the blower comes on, circulates the warm air and then the burners go off but the blower continues to go and that’s a cycle. Now, if the burner is coming on but going off quickly, then probably the thermal couple is worn out and that’s that piece of metal that’s usually right next to the flame. Sometimes the flame is sort of embedded into it. And when the thermal couple goes bad, that’s exactly the scenario that happens. You’ll light it; it will come on but then it won’t stay lit.

    So, at this point, you’re going to have to get the gas company or the HVAC service provider that you have in your area to come in and take a look at that because that’s part of the control circuit. It’s definitely not a do-it-yourself project but, at the same time, these types of repairs are typically fairly inexpensive.

    BETTY: So that means – that’s the reason why the pilot light goes out?

    TOM: Yes, because the thermocouple tells the pilot light to turn the gas on and if there’s no flame then the gas goes off. And so if the thermal couple is bad, the gas is just going to go off and not come on. It’s a safety system.

    BETTY: So it’s not the motor?

    TOM: No. The motor, you’re telling me, is running.

    BETTY: Mm-hmm.

    TOM: Yeah, so I don’t think it’s that. I think it’s a problem with the control circuit and it’s most likely the thermocouple.

    BETTY: Thank you so much. I think you saved me a ton of money. (chuckling)

    TOM: Well, you’re very welcome. Thanks so much for calling us at 888-MONEY-PIT. Stay warm.

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