Electrical contactor question

Discussion in 'HVAC Heating & Cooling' started by hidden 1, May 30, 2019.

  1. hidden 1

    hidden 1 Member

    Mar 13, 2009
    I finally got the 24 volt wiring to contactor going but still not engaging even if i direct wire the 3 24v wires at unit to bypass stat...Contactor is fairly new..
    Maybe the new part/coil relay helped.
    Defrost relay tested an seemed to work fine.
    4th capacitor at blower replaced also..

    Compressor engages when contactor button pressed .

    What should i look at next?
  2. hidden 1

    hidden 1 Member

    Mar 13, 2009
    I guess ill throw another contactor on it since they arent expensive..

    I also bypassed stat an direct wired ..

    Same thing..
    Anything else I should check if new contactor heeds same?
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Do you have an ohmmeter? Check the coil on the contactor. You cannot do this with power applied...remove the coil leads first. It will probably read in the low single digits of resistance. If it does and you've interpreted the wiring properly, applying voltage to it should energize it. If it's open, then the coil is inoperative.

    Using that multimeter, and connecting between the two wires attached to the contactor's coil, do you read 24vac? Remember, to work, you need a complete circuit...one that goes from one side of the secondary of the transformer, through the device, and then back to the other side of the transformer secondary. Measuring voltage can give you erroneous results if your reference points are not correct. For example, I was working on a high voltage power supply. The filaments ran on 5vdc. But, depending on how you measured it, it could either be 5vdc, or 4995 volts...the 5 volts was referenced to 5000, not ground.

    If the device energizes when you manually engage the contactor, at least the power contacts are wired properly.
  5. hidden 1

    hidden 1 Member

    Mar 13, 2009
    Thanks,yes i have a meter ..

    Got it going via direct wire O -R-Y-G..
    Contactor engaged-

    I guess theres a short in stat wire...

    Gonna install a better stat soon..
    At least i have updated a lot on it
    including bad transformer ,4 capacitors an 2 relays[1 was bad] !.

    Thanks again
    Last edited: Jun 5, 2019
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