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    markster2's Avatar
    markster2 Posts: 2, Reputation: 1
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    #1

    Oct 25, 2006, 06:02 AM
    Furnace cycling while heating
    I have a Tempstar hvac (heatpump) with a gaspack. It is about 9 years old. I turned the heat on for 1st time this year to discover the problem. I took the cover off to see this happening: I turn the thermostat up and the pilot is one. After a minute of so, the gas turns on and the furnace lights. The combustion blower is on. The main blower fan turns on and then the furnace goes out (leaving the pilot light). It does this over and over.

    I assume that the unit does not know that the main furnace flame is on. Does a compoent need to heat up or sense the flame? I have read through other questions, but am not sure what the problem is.

    Thanks.
    NorthernHeat's Avatar
    NorthernHeat Posts: 1,455, Reputation: 132
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    #2

    Oct 25, 2006, 02:17 PM
    Hard to guess, Is this a honeywell smart valve? It has 2 molex type connectors going into it. These valves are notorious for doing things like you describe.
    markster2's Avatar
    markster2 Posts: 2, Reputation: 1
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    #3

    Oct 25, 2006, 04:06 PM
    Thank you for the quick response. Yes. It does have a honeywell box with two molex type connectors plugged into it. I have attached a picture.

    The unit has been off and is cold. I turned it on. I did notice today that it stayed lit for several minutes the first time it turned on. The cycle times get shorter until it is on for just a few seconds at a time. During the cycling, once it is off, the igniter turns bright orange, the pilot is on, you can smell gas. It may or may not light. If it does not light, the system everything turns off and it tries again. Now that it is hot, if it does light, the main burner will be on for only a few seconds per cycle. I assume the clicking in the honeywell box is an internal relay. Any suggestions?

    Thanks.
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    NorthernHeat's Avatar
    NorthernHeat Posts: 1,455, Reputation: 132
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    #4

    Oct 25, 2006, 08:18 PM
    That's a smart valve, Good chance it is the cause. Yes, they are expensive.

    Let me know how it turns out.
    dhs's Avatar
    dhs Posts: 3, Reputation: 1
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    #5

    Oct 25, 2006, 09:24 PM
    If this problem goes on for a long time be prepared to change board as well. You will find it in lower part of the furanes at the blower
    NorthernHeat's Avatar
    NorthernHeat Posts: 1,455, Reputation: 132
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    #6

    Oct 26, 2006, 04:34 AM
    It sounds like just the gas valve is going bad. It won't get better, just worse.
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