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Outside air conditioning unit "click" sound when turned on/off


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  • Outside air conditioning unit "click" sound when turned on/off

    Hi all. Thanks for the opportunity for asking for some help! And thanks for reading!

    I have an old electric GE outdoor air conditioning unit, model TA936H, produced in March 1968, that was working recently but has since stopped working. The problem I am having is this: when I turn on the AC from the thermostat, there is one strong "click" sound that comes from the outdoor unit, then silence. It doesn't turn on or make any other sounds until I use the thermostat to turn it back off. When I do that, it clicks again. The furnace fan works. Just to clarify, I am not talking about the click sound that comes from the thermostat.

    I am comfortable working on the unit, and have in the past. (I replaced a leaking capacitor, as seen in the pictures below.) I have done some reading and it sounds like there could be a short in the system somewhere. I have pictures of the unit, but it looks like I need to have 15 posts here before I can link to those pictures. If you need them, I could possibly PM/email you the links. Any help or direction is appreciated! I will actively respond in a quick way.

  • #2
    I'm much more familiar with refrigerators, but I'd expect that the strong clicking sound you're hearing may be the start relay on the compressor motor operating.

    On refrigerators, and I don't know that they're all the same, when the thermostat turns the compressor on, the power that flows through the motor also flows through an electromagnet in the relay. Since an electric motor is essentially a dead short until it comes up to speed, the initial current draw by the motor is very high. Consequently, the electromagnet in the start relay is strong enough to pull a pair of contacts down which allows current to flow through the start windings in the motor.

    As the motor comes up to speed, the current draw becomes less and less, and the electromagnet in the relay loses strength until spring tension pulls the electric contacts apart again. This is what causes the start windings to lose power once the motor comes up to speed.

    So, from what you're describing, I think the start relay in the motor is working fine, and there wouldn't be power going through the electromagnet if there wasn't ALSO power going through the run winding of the compressor motor. So, I'd think either the problem is with the start capacitor or the start winding in the motor. I'd have the capacitor checked.

    Also, you might want to talk to someone who repairs GE central air conditioners to confirm that they use an electromagnetic relay to cut the start winding out as the motor comes up to speed. I just know that many fridges do, and it wouldn't surprise me to see the same type of system on an air conditioner.
    Last edited by Nestor; 07-09-2012, 06:52 PM.


    • #3

      Commercial air conditioners use 24 volts as the control circuit wiring. all contactors use a 24 volt AC coil. A hermetically sealed compressor uses a start relay that is current sensitive. As Nestor stated, any motor presents itself as a dead short when it starts drawing as much as 135% of nameplate current. As the motor spins up to running speed this current reduces and eventually cuts out the start winding because of action of the start relay. The compressors also have buried in the windings, thermal overloads that open the control circuit if too much heat is created. Some compressor like the copeland have a klixon overload bolted to the external shell to detect this heat and opens before severe damage happens to the compressor. Lack of or low freon in the system will overload the motor causing high currents and heat. Also, lubricating oil for R-22 flows with the freon to remove heat and lubricate the compressor's piston and motor bearings. No oil will cause overheating. For safety, I would install a freon sight glass in the system so you could see "air bubbles" in the freon flow, if there was any. Perhaps your filter/dryer is clogging up.