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    kjaymak's Avatar
    kjaymak Posts: 2, Reputation: 1
    New Member
    		  
    #1

    Jul 8, 2007, 08:19 AM
    Fan shuts on and off
    I replaced the thermostat,fan limit control switch, and still when a/c is turned on the fan shuts on and off every 30-45 second intervals, sometimes it will run contiuously, sometimes it won't. And when I say the fan limit control switch It's the part that has pointers on it for dgree on start and shut down. Any help would be greatly appreciated thanks. It`s a Lennox furnace, I had a a/c contractor come in and he did the replace meant parts. Problom not solved, contractor will not come back with out billing me another service call. When I explain the problem to other contactors they won't touch it... could it be the fan motor? There is no fan relay switch on this system. Why I do not know , but fan setting is on high speed,(needed for a/c).
    acetc's Avatar
    acetc Posts: 1,004, Reputation: 79
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    #2

    Jul 8, 2007, 02:43 PM
    Yes it could be the motor, can be checked with a volt meter on the wires to the motor to verify constant voltage to the motor when the motor shuts down, could be a run capacitor on the indoor motor (much cheaper then the motor) Could also be the fan relay which is a different componet then the fan- limit switch. The fan-limit switch works in conjunction with the heat to bring on the fan during the heating mode and shut off the gas valve (limit) should the furnace overheat. Mike
    hvacservicetech_07's Avatar
    hvacservicetech_07 Posts: 1,083, Reputation: 75
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    #3

    Jul 8, 2007, 03:32 PM
    What is the model number of the furnace?
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