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

    Nov 8, 2011, 09:18 AM
    Coleman Furnace #7975a856 has its pilot light on, but will not start
    I am having problems with my Colman furnace. The pilot light is on, But when turning on the thermostat
    I hear a click but that's it. No burner flame. I jumped the R & W wires to check the thermostat, but in
    Putting power back to the furnace, nothing happens. Also checked power of the transformer. I have 110v
    To the 110V side and have 24V going out to the lower limit switch, but not on the other 24V side going to
    The thermostat. Could it be the Transformer? Or anything else.
    Greg H
    drtom4444's Avatar
    drtom4444 Posts: 3,282, Reputation: 145
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    #2

    Nov 9, 2011, 01:29 AM
    Dis you check the resistance of the gas valve coil? It sounds like it is open. DrTom4444
    GregHettinger's Avatar
    GregHettinger Posts: 3, Reputation: 1
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    #3

    Nov 9, 2011, 01:22 PM
    No. Not sure where that is. Is it right on top of the gas valve, with one wire going to the Aux. limit switch
    And the other going to the thermostat? Should it be showing resistance? Greg
    drtom4444's Avatar
    drtom4444 Posts: 3,282, Reputation: 145
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    #4

    Nov 9, 2011, 03:14 PM
    The coil on the gas valve is where there are two wires going into it. When your unit is calling for heat there should be 24-30 volts going to those two wires. When measuring resistance you have to disconnect the wires and put the meter on ohms and read across the two terminals. If you get an open connection you need a new gas valve. DrTom4444
    drtom4444's Avatar
    drtom4444 Posts: 3,282, Reputation: 145
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    #5

    Nov 10, 2011, 07:02 AM
    To answer your question on the limit switch- the limit switch should show zero resistance. If it's open then you need to reset it and find out why it tripped. A bad fan motor will do this as well as poor air flow, such as a stopped up air filter. You need to trace the voltage to make sure you are getting voltage to gas valve. It's very simple. DrTom4444
    GregHettinger's Avatar
    GregHettinger Posts: 3, Reputation: 1
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    #6

    Nov 16, 2011, 12:48 AM
    I installed a new Gas valve, but now I don't have any gas coming out of the valve to the pilot.
    I disconnected the pilot tube to check to see if gas is even coming out the valve but I get nothing.
    I changed around everything to covert to LP. Is there something I'm missing to do on the valve
    That might me blocking the flow of gas?
    drtom4444's Avatar
    drtom4444 Posts: 3,282, Reputation: 145
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    #7

    Nov 16, 2011, 01:14 PM
    Did you test the valve before you replaced it? Are you getting 24 volts to the valve? You need to check out the electrical circuits before you do anything. DrTom4444
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