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Troubleshooting a Dehumidifier

Discussion in 'General Off Topic Forums' started by toxcrusadr, Jun 3, 2017.

  1. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    Sorry for the slow reply, I got busy and haven't got back to this. Thanks for the analysis Mark.

    Questions:

    1) the fan does come on, just the compressor doesn't. Is your test (triggering pins 5,6, or 7 with +5V) still necessary? It seems that if the brain board is turning on the fan then +5V is going to the brain board which is the purpose of the test.

    2) "...trigger pins 5 6 or 7 on THIS board using a jumper to +5v (pin 3 of CN14 or better yet the + of C3) to engage each relay separately..." On your labeled drawing above, pin 2 is +5V and pin 3 is +12V. Are we using 5 or 12V on pins 5, 6 and 7? I believe that's 5V and pin 2....or is it 12V and pin 3? ;)

    In an earlier post it looks like I said the 12V regulator was 7812a. Seems like the other one was 7805 but I'm not at home at the moment. I can get a better pic of the top also.

    Really appreciate everyone's help. Humidity is bad and I've got an ancient 80s unit going that's on its last leg!
     
  2. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    more pix of that board unnecessary for now.

    You caught my pin 3 / pin 2 error. It's pin 2, and 5 volts. 12volts might be too "hot".

    #1. test is necessary - just because the fan works doesn't mean the works aren't jammed up for the compressor on the relay board
    The TEST is that we need to see the compressor operate from a 5v logic signal on pin 5,
    to verify TR3 is ok, and even to the level that the 12v substitution you used didn't hurt anything.
    Disconnecting the brain board for the test is to prevent damage to the brain board from the pin 5 signal being substituted.
    Pins 6 and 7 being operated successfully also tests both the board and the method in case pin 5 didn't operate.
     
    Last edited: Jun 15, 2017
  3. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    One we verify the board, then we consider why the brain isn't turning on the compressor.
    The logical first thought is the humidity sensor on a separate little board.
     
  4. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    Location:
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    Got it. I'm away for the weekend so it looks like it'll be early next week before I can get to it. Just so you know I'm not blowing off the help. :biggrin:

    The humidity sensor is indeed on a tiny board of its own, I had to unscrew it from the front cover of the machine to remove the cover.
     
  5. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    Gotcha, no problem. slow but steady wins the race.
    Tell ya whut, PM me to wake me up when you are continuing the thread, then I won't be forever checking back in to see if anything's posted new.
     
  6. markshan

    markshan Sir Thrift a Lot Subscriber

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    Last edited: Jun 22, 2017 at 9:24 AM
  7. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    First - my suggestion: new thread, this is an active thread.
    second - try a different GFI - they can get squirrely.
     

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