George (geo999)
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Thread: George (geo999)

  1. #1

    Confused George (geo999)

    Inside- Difficult (for me) AC problem. Bryant central AC ONLY unit Legacy 123R 44K BTU 3.5 not working. Blows room temperature or slt warm air when on. When AC thermostat calls for AC, condenser fan turns on and runs normally. The compressor usually does not start. When it does it runs for only 10-15 minutes and shuts off. Have had service techs out 3x's. Added 2 lbs R-22. They did not check for a leak!!! Changed thermostat batteries and thermostat is working properly. 24 volt thermostat transformers are all reading proper input and output voltages W DMM. Cold and heat transformers all checked w DMM. Internal on furnace AC relay working. Internal control board connections tightened and swapping out relay to board had no effect.

    Outside - voltage at L1 and L2 245vac in spec. Tried replacing very charred contactor w new one worked for 1-2 days then repeat of same problem. New contactor also became pitted and charred. Check capacitance of Turbo 200 start/run capacitor - checked out nominal set at 60 - herm and 7.5 fan. even bought new one and tried it again same issue. With contactor engaged and unit on 24-25 vac at contactor terminals and vac at L1, L2 - Load 1 and Load 2 approx 245-247 vac.

    I have the compressor exposed and will relay readings from C,R,S and to each to ground.

    R to C = lowest reading 0.5 u
    S to C = middle reading 1.8 u
    S to R = Highest reading 1.4 u

    Lowest + Middle = Highest 0.5 + 1.8 = 2.3 not 1.4

    Resistance from C,R, S to ground range from 1.1 to 11 Mu very low = Grounded Motor

    When the compressor does run it sometimes runs normally for a while. Most times it does not run at all or runs very loud and makes a groaning sound like the motor/pump is having difficulty turning.

    So far - condenser coils, evaporator coils have been cleaned and are OK. Replaced air handler filter. Also had faulty limit control switch was replaced and is working normally after testing.
    The new fan limit and contactors are the identical replacements for the worn out original parts.

    My conclusion is that the compressor motor is grounded and needs replacement.

    Please provide any comments and further insight. I am worried about the recurrent burning of the contactor. Would a grounded motor cause this? It is expensive to replace the compressor but somewhat less expensive that replacing the whole unit < 5 years old. Not in Warranty because I was not aware there was one and never registered it w Bryant.

    Will only be in the house for 2-3 years.

    Thanks
    George

  2. #2
    Addendum to note - the reading for the R,S,C terminals in prior post wrong the following are correct:
    R to C - 0.5 u
    S to C - 1.5 u
    S to R - 2.0 u
    Checks out OK.

    The readings from R to Gr - 25 Mu S to Gr - 9.3 Mu C-Gr - 5.5 Mu all seem very low. Is the motor grounded and needs to be replaced?

  3. #3
    The readings re r to ground all very high but not infinite. What is the proper interpretation of the readings from 5-25 million ohms?

  4. #4
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,627
    George take a moment and read the site rules. You're not likely to get answers to those kinds of questions here.
    http://hvac-talk.com/vbb/showthread....ad-these-rules

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