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    marragtop's Avatar
    marragtop Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Jul 11, 2014, 05:21 AM
    Central A/C problem
    Hi: I'm new to this site and of course I have a problem. I have a Trane 14XLI unit that the AC stopped working on yesterday. The outside unit just hums. The fan is NOT locked up and will engage and run if I push start it. But still no cold air. I suspect the compressor is not kicking on. I realize that push starting the fan is esentially bypassing the capacitor. Now my questions: are the fan and the compressor controlled by the same capacitor? I took the side cover off and can only see I capacitor. Is there a way to temporarily bypass the capacitor to see if the compressor will run? Thanks in advance for any responses.
    hkstroud's Avatar
    hkstroud Posts: 11,929, Reputation: 899
    Home Improvement & Construction Expert
    		  
    #2

    Jul 11, 2014, 05:59 AM
    Welcome to the site maraqtop.
    I am not an A/C tech and perhaps I should not respond but I will anyway.

    I have never seen an AC that used the same capacitor for the fan motor and the compressor. The capacitance required for each is vastly different.

    push starting the fan is esentially bypassing the capacitor
    I'll disagree with your way of stating that. Since the fan motor capacitor is a start capacitor, when you spin the fan, you are not by passing capacitor, you are doing its job of aiding the fan motor in getting started. Once the fan motor is up to speed the capacitor is taken out of the circuity.

    Since the compressor motor is enclosed in the "can" there is no way to physically or mechanically do the same for the compressor.

    Trace the wiring from the capacitor to determine if it is for the fan or the compressor. There is usually a big difference in the physical sizes of the two.

    Put your hand on the compressor. You should be able to feel the vibration and heat if it is running.

    The humming you hear is probably the compressor running.
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