Results 1 to 9 of 9
  1. #1
    Join Date
    Dec 2007
    Location
    north suburbs of Chicago
    Posts
    513

    Finally caught the devil!

    Four trips. Long time client called now and again saying that once in awhile the blower would start making all kinds of racket for a short time and go away. It only would happen on cooling or when she switched to fan on. This was before fan on powered a third choice in speeds.

    Three times I go or stop on the way to other calls and nothing and nothing to even consider would be causing it. I told her if just once I can get over and actually hear the problem I will know for sure what it is.

    Sure enough on the fourth trip the control board relay was freaking out powering the fan on and off about ten times a second before the fan caught and ran. First time I have seen this.

  2. #2
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,145
    Check the thermostat/input voltages on Y & G terminal.

  3. #3
    Join Date
    Dec 2007
    Location
    north suburbs of Chicago
    Posts
    513
    Quote Originally Posted by 54regcab View Post
    Check the thermostat/input voltages on Y & G terminal.
    Replaced the board and it's solved. I also replaced their T87 that had 9 yrs of cig smoke only because they wanted to. I doubt it was in the subbase because I cleaned those little BB contacts the very first trip.

  4. #4
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,145
    Bad board makes sense. I figured it was one or the other. I wouldn't be surprised it the smoke took out the board, I've seen it corrode the copper traces.

  5. #5
    Join Date
    Sep 2011
    Posts
    59
    Same thing happened to me. Customer called about a noise, I couldnt duplicate it, called back saying it was happening again, I went back, couldnt duplicate it and everything checked out.... On the 4th callback I stayed for almost 2 hours crawling in the attic, checking condenser, wiring, board etc until...... IT HAPPENED!!!! relay stared clicking moderately fast until the blower would catch on, and then, every so often it would shut blower off and click again for a minute or so until the blower came back on... Very very annoying to not be able to duplicate the problem for so long... Live and learn I guess....

  6. #6
    Join Date
    Dec 2007
    Location
    north suburbs of Chicago
    Posts
    513
    Quote Originally Posted by gesellman View Post
    Same thing happened to me. Customer called about a noise, I couldnt duplicate it, called back saying it was happening again, I went back, couldnt duplicate it and everything checked out.... On the 4th callback I stayed for almost 2 hours crawling in the attic, checking condenser, wiring, board etc until...... IT HAPPENED!!!! relay stared clicking moderately fast until the blower would catch on, and then, every so often it would shut blower off and click again for a minute or so until the blower came back on... Very very annoying to not be able to duplicate the problem for so long... Live and learn I guess....
    Yep. It's one of those calls like many that you have to be there when it happens. If I run into it again I'll just tell em let's try a board. I'll leave the old one here and if I'm wrong I can put it back in. Like I said it's the first time ever for me.

    I once replaced a defective Bryant/Carrier 3 wire pilot with (as it turned out) a POS generic one.
    The lady said once in awhile the furnace is making crazy sounds. The POS generic was clicking the main gas on and off so fast that the gas was burning in the venturis! Another that had to happen while I was there finally.

  7. #7
    Join Date
    Jul 2005
    Location
    Boston/Cape Cod
    Posts
    66
    Quote Originally Posted by Glennhvac View Post
    Yep. It's one of those calls like many that you have to be there when it happens. If I run into it again I'll just tell em let's try a board. I'll leave the old one here and if I'm wrong I can put it back in. Like I said it's the first time ever for me.

    I once replaced a defective Bryant/Carrier 3 wire pilot with (as it turned out) a POS generic one.
    The lady said once in awhile the furnace is making crazy sounds. The POS generic was clicking the main gas on and off so fast that the gas was burning in the venturis! Another that had to happen while I was there finally.
    Sometimes that's the best thing to do, that gut feeling. I do a lot of oil fired equipment and many times the customer can tell me what is wrong even throe they don't know it, without me wasting two hours trying to get all the stars to line up again.I explain just like you did, I'm about 99% sure but just it case..........
    southshorejohn

  8. #8
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    913
    I'm experiencing something very similar this last week. Another tech has been out once, I've been out 3 times. Went yesterday with the boss. Customer recorded the sound and it sounds like a siren for less than 5seconds and all is normal. It never happens where we're there.

    All the duct work is behind drywall, except for the plenum. Its driving us up the wall but I don't think its a mechanical noise......

  9. #9
    Join Date
    Dec 2007
    Location
    north suburbs of Chicago
    Posts
    513
    Quote Originally Posted by johnt2_2002 View Post
    I'm experiencing something very similar this last week. Another tech has been out once, I've been out 3 times. Went yesterday with the boss. Customer recorded the sound and it sounds like a siren for less than 5seconds and all is normal. It never happens where we're there.

    All the duct work is behind drywall, except for the plenum. Its driving us up the wall but I don't think its a mechanical noise......
    Ok maybe not but........
    There was this device made that went on the r/a duct that would whistle when the filter got dirty. For all I know it sounded like a siren.

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