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    Barnabay's Avatar
    Barnabay Posts: 3, Reputation: 1
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    #1

    Oct 3, 2009, 05:34 PM
    Coleman 7900 mseries furnance/mobil home
    My furnace come on even though the stat is not wanting heat,the only way to shut it down is to manualy turn it off at the furnace
    hvacservicetech_07's Avatar
    hvacservicetech_07 Posts: 1,083, Reputation: 75
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    #2

    Oct 3, 2009, 05:58 PM

    Remove the cover on the thermostat, make sure no wires are touching or shorted together. Remove the white wire from the W terminal, does that shut it off?
    Barnabay's Avatar
    Barnabay Posts: 3, Reputation: 1
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    #3

    Oct 3, 2009, 07:07 PM

    No,this does not do anything,the blower and burner come on,even when the stat is not connected
    wmproop's Avatar
    wmproop Posts: 3,749, Reputation: 91
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    #4

    Oct 3, 2009, 08:21 PM
    Make note of where what color wire is connected to and disconnect the tstat wires at the furnace,, see if that stops it from running,, if it does you prob. Have shorted tstat wires, you might have to replace the wires to correct the prob. shouldn`t be to hard in a mobil home
    hvacservicetech_07's Avatar
    hvacservicetech_07 Posts: 1,083, Reputation: 75
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    #5

    Oct 3, 2009, 08:21 PM

    Trace the low voltage wires, something is shorted.
    Barnabay's Avatar
    Barnabay Posts: 3, Reputation: 1
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    #6

    Oct 4, 2009, 05:05 AM

    Would a bad limit switch cause the problem?
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #7

    Oct 4, 2009, 08:50 AM
    If yours is the old style control system (a heat/off/cool switch on the furnace) one of the relays in the compartment is stuck in the heat on position.
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