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  1. #1
    Join Date
    Sep 2004
    Posts
    265

    Problems with potential relay

    Walk in cooler, Tecumseh compressor AKA9442EXD, R-22.

    Customer calls walk in cooler warm compressor hot. I check unit and find the potential relay contacts not opening and further inspection find the relay coil open. I go get new start components, install and the unit is doing the same thing, relay contacts not opening, compressor pulling 16 amps.
    Potential relay was crossed to a Mars 19163 per the manufacture.
    The comp will only run about 20 seconds before going out on the ext overload. What am I missing? Any help or suggestions appreciated.
    Also customers says a day before the cooler had trouble they had a power surge.

  2. #2
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,611
    What's it supposed to be pulling, amps-wise? Run capacitor OK? Start winding OK? Overload OK? Start relay dropping out correctly?

  3. #3
    Join Date
    Sep 2004
    Posts
    265
    According to Tecumseh spec sheet RLA 4 amps, LRA 31.
    Start relay was found to be bad, all start components were replaced including run cap.
    C-S = 2.3
    C-R = 1.9
    R-S = 4.1

  4. #4
    Join Date
    Feb 2007
    Location
    Ohio
    Posts
    205

    double check...?

    I've had bad start components right out of the box, I'd check the caps again to start off. Once the compressor is running pull one wire off the start cap and watch the amperage, all your doing by this is dropping out the start manually. I've also had maufacturers do a bad cross reference over the phone but highly unlikely.
    I'l probably catch hell for telling you to risk life and limb by disconnecting power, loosen the spade terminal to the single wire spade connector to the start cap, apply power, let compressor start, usng a needle nose pull the loosened connector off the start cap and check amperage but what the hell.

    js

  5. #5
    Join Date
    Dec 2008
    Location
    Dixiana, AL
    Posts
    2,611
    I think you've found your problem, per the resistance readings you've given. This is another one of those rule of thumb issues that has a correct answer if you go to the mfg on a specific motor, but the issue is that your C-R and C-S are too close together. Looks as if you have a shorted winding.

    Found my ROT: C-S is normally 3 to 6 times higher than C-R.

  6. #6
    Join Date
    Feb 2007
    Location
    Ohio
    Posts
    205

    looks like it..

    Quote Originally Posted by klove View Post
    I think you've found your problem, per the resistance readings you've given. This is another one of those rule of thumb issues that has a correct answer if you go to the mfg on a specific motor, but the issue is that your C-R and C-S are too close together. Looks as if you have a shorted winding.
    It is awfully close...

    js

  7. #7
    Join Date
    Oct 2008
    Location
    Canada
    Posts
    83
    According to my Techumseh book.. AK9442E @ 77*F

    S-C 9-12

  8. #8
    Join Date
    Jun 2009
    Posts
    100
    checking potential relay or start components

    I keep saying I want to make a rig with a momentary switch this could be used like a hard start to turn a compressor or check pot relay

  9. #9
    Join Date
    Aug 2009
    Location
    SW Missouri
    Posts
    16
    Was there ever a final determination of what was wrong with the compressor or it's start components? Terminal readings didn't look right to me. Just curious

  10. #10
    Join Date
    Sep 2004
    Posts
    265
    Quote Originally Posted by Bobalooh View Post
    Was there ever a final determination of what was wrong with the compressor or it's start components? Terminal readings didn't look right to me. Just curious

    It was the compressor. Readings were way to close. The relay was bad which is probably what did in the compressor. New compressor and drier all is working well.

  11. #11
    Join Date
    Aug 2009
    Location
    SW Missouri
    Posts
    16
    Thanks for the update. I don't deal with many compressor failures on ice merchandisers but when I do I try to understand why they failed and gain any knowledge from testing them. Thanks

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