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No Power to T-Stat after replacing condenser motor


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  • No Power to T-Stat after replacing condenser motor

    My condenser motor burned up on my condensing unit, so I went to replace it. After replacing both the motor and the capacitor, I returned indoors to switch the thermostat from "off" to "cooling". The display was dead, and the stat has not turned back on (about 1 hour now). I had the disconnect for the condensing unit in the off position while I was working on it, and it was in the off position for about 2 days (the thermostat was working fine during this period). Any suggestions on what could have caused this issue? I did not mess with my indoor unit, and the 24 VAC step-down transformer is located in this unit. Thank you in advance for your help on this issue.

  • #2
    Update: T-stat is now working; I had to flip the switch on my stepdown transformer inside my indoor unit. Now I have another problem: The condenser fan shut off. It was running for a solid hour before I heard a loud unfamiliar hum. When I investigated, the fan was off and the compressor was running. I shut everything off, re-wired the capacitor, and tried again. Now I cannot get the fan and the compressor to turn on together. Any help would be appreciated. The installed parts are as so: Motor: Grainger part number 4MB21 Capacitor: Grainger part number 5CMZ7 One guess I have is that the motor says it requires a 370 VAC capacitor, but I purchased one like the original @ 440 VAC. Besides that, everything is the same in the capacitor. Assistance?


    • #3
      condenser fan

      the capacitor should have a voltage rating of the original or higher, never lower. the value in microfarads should be the same, again never lower than the original. its function is to offset a pahse so the motor will spin. the capacitor connection uses a brown or brown/white colored lead to the white - neutral. the black goes to the contactor.