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  1. #1
    Join Date
    Sep 2010
    Location
    Indiana
    Posts
    365

    Burnt smell from vents

    I have a call from a customer that is telling me that they turned the AC on yesterday night and had a burnt wiring smell coming from the vents.

    This is a Rheem heat pump and strip heat. My first thought was that he was heating and the strips came on for the first time of the season. He insists that the house was 77 and they turned on the AC.

    Then he says that he shut it off and started it back up a few minutes later and cold air wasn't coming out of the vents. I asked if there was air coming out that wasn't cold or no air?

    I was told the air flow was good but not cold... That should eliminate the indoor blower motor.

    I was just there 3 weeks ago pulling the indoor coil and scrubbing the mold off.... So I'm wondering what I'm getting blamed for....

    Aside from strip heat and indoor blower motor, what else would cause a burning wiring smell...

  2. #2
    Join Date
    Jun 2009
    Location
    Pompano Bch, S Fla
    Posts
    57
    Umm...a burned wire Sorry couldn't resist. Obviously it's low voltage, maybe Y was rubbing on metal inside the cabinet and finally got through the insulation. Although that would likely have shorted the transformer. Maybe a bad relay. In any case if you were there 3 weeks ago and it just now happened it's probably an unrelated issue.

  3. #3
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,486
    Xmfr

  4. #4
    Join Date
    Jun 2009
    Location
    Pompano Bch, S Fla
    Posts
    57
    If ti was the transformer the fan wouldn't run

  5. #5
    Join Date
    Mar 2012
    Location
    Birmingham Al
    Posts
    256
    two weeks ago i ran into the same thing, it was actually the blower motor causing the smell water source package unit opened top blower motor winding had a light black coating on them smell was very strong. the capacitor was weak changed capacitor motor amps went down .5 amps and smell stopped. informed customer that the motor may soon go out and they opted not to change at this time. have not heard back from them.

  6. #6
    Join Date
    Jun 2012
    Location
    nampa idaho
    Posts
    66
    Had the same problem and it was the blower motor, did you check the amp draw

  7. #7
    Join Date
    Sep 2010
    Location
    Indiana
    Posts
    365
    I've been without internet for a few days, but it is up and running now.

    I stopped by this unit on my personal time just to do a quick check. I didn't have any meters, but was blowing warm inside and the condenser fan was off. I cycled the defrost test pin (in a/c mode) a few times and it went back to normal.

    I came back with tools and meters two days later and a defrost board and could not for the life of me get it to duplicate the problem.

    I tapped on the thermostat and defrost board, checked inside the air handler and could not find and issue. I thought maybe it was losing the reversing valve voltage, but it is a rheem.

    Anyone ever have a defrost board fail during a/c mode and go into defrost mode?

  8. #8
    Join Date
    Apr 2001
    Location
    Over Here
    Posts
    1,105
    Amp the air handler incoming power. It is common to have the sequencer stuck and engage a heat strip or two. We see this at least once every couple of weeks. You speak of Rheem... don't know if your unit has the cal-rod heaters, or strips. I have seen a portion of the strips ground out and draw current between one hot leg and ground, or a piece of sheet metal or silver tape that fell on the strips inside do similar. Amp out each leg... Any more than the blower amp draw should be suspect.

  9. #9
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,962
    Burning smell, heaters not energized, blower operates, cooling does not operate.....

    The burning smell could still have been from the blower, but then why would the cooling now not operate?

    There should be nothing in the air handler to control the outdoor unit other than a wire nutted or terminal screwed connection for Y from the stat to the outdoor unit, I would look for something shorted in the Y circuit.

    Just for an out in left field possible scenario, make certain that the blower does not operate if the thermostat is in the cooling mode but not calling for cooling and the fan switch is not in the on position on the t-stat. What I am thinking is if something got stuck in the heating coils, causing the burning smell and the blower to turn on through a limit switch.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  10. #10
    Join Date
    Nov 2011
    Location
    Philadelphia, PA
    Posts
    202
    Quote Originally Posted by Pete954 View Post
    If ti was the transformer the fan wouldn't run
    i had a blown fuse on a goodman furnace a few weeks ago and fan ran continuously until fuse was replaced.

  11. #11
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,528
    I suspect blower motor or heat strips. As stated, check AHU amps.

    I have had a faulty defrost control causing "w" to be energized all the time.

  12. #12
    Join Date
    Sep 2010
    Location
    Indiana
    Posts
    365
    I believe this one to randomly enegergizing W and shutting down the condensing fan.

    I appreciate all of the input. I hope not to have a call back, but if it acts up again I'll have several good points to check.

    I wish it would have acted up while I was there with my tools.


    BTW... Does anyone make a universal demand defrost board?

  13. #13
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,528
    I'm not familiar with Rheem. But I assume they use a demand defrost. I would ohm out your coil temp and ambient temp sensor. If they are faulty (or incorrect), it could be going into a random defrost.

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