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Thread: Strange Problem

  1. #1

    Strange Problem

    Good day. This is my first post here. I have been in the hvac/r field for about 6 years now. I have came across something that I have never incountered before. Here is the run down.

    My brother-inlaws ac unit is an older coleman single stage electric/gas package unit. He had a new heat exchanger put in last year. Ran great during the winter months. Switched to cooling mode and got nothing. I showed up with meters in hand. I didnt have control voltage. Replaced the transformer. The control voltage is now back. I can get the indoor fan to run, the gaspack will run, but when you switch to cooling, you get nothing, but a blown transformer. Replaced the transformer, and put an inline fuse in to protect it. I can get the compressor to run by manually pushing in the contacts.

    I put my meter on the red wire and the yellow and had continuity. Jumping the gun, I pulled a new wire thinking there was a dead short in the jacket. After new t-stat wire pulled, still have continuity between the two wires. Now, If I pull the moulex plug of the control board, I lose the continuity between the red and yellow wires. Also, if I remove any wire off of the contactor, I will lose the continuity also. I have replaced the contactors, the start/run caps. I have pulled the whole harness out, there is no chared or broken/skinned wires. My brother inlaw is limted on money. I pulled the boared, and checked it over. The board looks good, and works for everything, but the cooling. We also put on a new t-stat. Before I order a board, would anyone here know what might be my "gremlin".

    Like I have typed above, I have never hit a bump like this. The only thing left in the cooling circuit that hasnt been renewed is the board. Any help would be greatly appreciated.

    Thanks,
    Brad

  2. #2
    Join Date
    Feb 2008
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    Western NC
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    wow......

    you've tried looking for the dead short? And couldn't find it.

    So why did you replace the caps? they are not control circuit. You need to go back to the basics. Rule everything else out by testing it, not just throwing a new one in. You could be replacing a bad part with another bad part. Ever think of that?
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  3. #3
    Quote Originally Posted by iraqveteran View Post
    wow......

    you've tried looking for the dead short? And couldn't find it.

    So why did you replace the caps? they are not control circuit. You need to go back to the basics. Rule everything else out by testing it, not just throwing a new one in. You could be replacing a bad part with another bad part. Ever think of that?
    I replaced the cap because an electrican friend was with me, and sugested that the cap was over amping and feed back through the system. Didn't make since to me, but I had it on the truck, so throwed it on. I have traced all the wires, there isn't any bare or melted wires. Nothing going to ground. I went as fare as taking each wire off, set my meter to continuity, put one lead on the end of the wire, then touched ground. No continuity anywhere, with the exciption of the board. I also took the t-stat wires off the board terminal strip. There is continuity between red and yellow. Again, removed a wire off the contactor, or remove the moulex plug, I lose the continuity.

    I checked the contactor with my meter. I have resistance on the coil, the contacts are clean. I just went over to his house(he is only a few minutes away) I have continuity across the contacts with the contacts opened and closed. Could I have gotten a bad contactor off the shelf?

  4. #4
    Join Date
    Feb 2008
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    Western NC
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    Quote Originally Posted by badams201 View Post
    I checked the contactor with my meter. I have resistance on the coil, the contacts are clean. I just went over to his house(he is only a few minutes away) I have continuity across the contacts with the contacts opened and closed. Could I have gotten a bad contactor off the shelf?
    seems that way.....

    you checked to ground.....how bout to common. Did you isolate all the wires first?
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  5. #5
    Join Date
    Apr 2008
    Location
    Southern New Hampshire (USA)
    Posts
    401
    When you say you have continuity across the contacts, are you referring to the high voltage contacts (l1,l2,t1,t2), or the coil contacts? Because the resistance through the coil contacts would not change wether the contactor is open or closed. Also, if you are not getting continuity through your control circuit for the compressor contactor, did you ohm your LPCO and HPCO?

  6. #6
    Join Date
    Apr 2008
    Location
    Alberta Canada
    Posts
    2,246

    get professional status first

    Then we can help. How do we know if you are not DIY. Read rules.
    Do it right the first time.

  7. #7
    Quote Originally Posted by 21degrees View Post
    Then we can help. How do we know if you are not DIY. Read rules.

    Thanks for the help...........or the lack of. I ohmed out the board. There was a few shorted componets on the board.

    By the way, I am not a DIYer. I work for a hospital maintaining the high pressure boilers and chillers. Been doing this for nearly 7 years. I didnt think it was the board, due to the board had no sign of being bad. It is ok that you all didn't know how to help me, but you didn't have to get all crazy on me. Hope you all have a great day.

  8. #8
    Join Date
    Dec 2006
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    *

    Quote Originally Posted by badams201 View Post
    Thanks for the help...........or the lack of. I ohmed out the board. There was a few shorted componets on the board.

    By the way, I am not a DIYer. I work for a hospital maintaining the high pressure boilers and chillers. Been doing this for nearly 7 years. I didnt think it was the board, due to the board had no sign of being bad. It is ok that you all didn't know how to help me, but you didn't have to get all crazy on me. Hope you all have a great day.

    if you think that they went crazy on you, hang around for a little while and you will see crazy!

    as stated apply for pro membership, we would love to "get all crazy" on you in the pro section



    .

  9. #9
    Join Date
    Jan 2004
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    Quote Originally Posted by Airmechanical View Post
    we would love to "get all crazy" on you in the pro section



    .
    Leave your after hours personal life out of it. LOL...
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  10. #10
    Join Date
    Dec 2004
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    200
    Who got crazy? lol, I dont know why but when you said that I busted out laughin. I dont even know why it was funny but it was.

  11. #11
    Join Date
    Nov 2004
    Location
    North Carolina
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    Quote Originally Posted by badams201 View Post
    Thanks for the help...........or the lack of.

    It is ok that you all didn't know how to help me, but you didn't have to get all crazy on me. Hope you all have a great day.
    Guy's, sounds like ya'll have hurt his feelings! Here I thought everyone was being extra kind! Now that the OP has confirmed that no one else here knows what they are doing, I don't feel so alone! lol

    FYI - (OP) There are more smarts here than you can shake a stick at, but rules are rules so you need to get your post count up and move over to the pro forum's. You can't think of a HVACR question that won't get answered in detail there. Question is - Are YOU tough enough?

  12. #12
    Join Date
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    Quote Originally Posted by beenthere View Post
    Leave your after hours personal life out of it. LOL...

    are you having those crazy thoughts again, i thought you got over that!



    .

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Quote Originally Posted by Airmechanical View Post
    are you having those crazy thoughts again, i thought you got over that!



    .
    My doctor says I'm doing much better.
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