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When my air conditioning comes on, I hear a loud buzzing and notice the condenser fan is barely spinning or not spinning at all. I used a Fluke 88 to measure capacitance on the start/run capacitor separate from the system, and it measures within a few percent of the label. I have the full 230v going to the fan terminals, so I assume I have a faulty motor.

My question is how do you choose a replacement motor? I have a GE 5KCP39JFV504S currently, and I'm assuming I would find an aftermarket replacement by a different manufacturer. I know I need a 230v 1/4HP 830RPM CW spinning motor, but other than that I don't know how to shop for one that will fit the blades and cover grate properly.

Condenser Fan Label

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Recheck your contactor in the compressor cabinet and make sure it's functioning properly and making contact. A buzzing can mean a bad contactor.

Your best bet for a replacement motor is to bring it into an AC parts and supply company or an electric motor supply place. They will match the RPM's, shaft size, rotation, frame size, wiring harness,ETC. Bring the motor with you. In many cases they can test the motor for you. Do yourself a favor and don't try to replace it online. They will tell you it will fit, and believe me, it won't.

You might want to consider replacing the contactor since you'll be shopping for a motor anyway. They're only about $15 bucks

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  • Hmmm...I'd do a bit more diagnostics. Like get an amp clamp and see if the motor is drawing the correct amount of current. From the nameplate it looks like it should be drawing 1.5 amps. If lots more than that, probably shorted windings which does mean a motor replacement. If too low, something else is going on. You said you checked the capacitor, you sure it's OK? – George Anderson Feb 29 '20 at 18:58
  • @GeorgeAnderson Many of the supply places I deal with will test the motor right at the counter... Yes, more diagnostics is always good. – JACK Feb 29 '20 at 20:16
  • Thanks Jack: That's where you guys who actually work in the trade can contribute so much. I'm just a decent DIYer that can ocassionally contribute. – George Anderson Feb 29 '20 at 20:40
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    Sounds like I need to find a supply place. I opened up the junction box, and verified there is 240v at the motor connection. Measuring voltage on the 5MF cap shows ~315v but the motor barely spins. I did verify the contactor shows no voltage drop when engaged. – Jeff Feb 29 '20 at 22:54
  • @GeorgeAnderson You've had some really good answers... keep it up. – JACK Mar 1 '20 at 14:56

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