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  1. #27
    Join Date
    Nov 2009
    Location
    Kansas City
    Posts
    124
    Did u put a manometer on to see what the differential pressure is? Checking for debris doesn't mean anything

  2. #28
    Join Date
    Sep 2010
    Location
    Gering, NE
    Posts
    14
    I had a older Lennox unit doing the same thing a couple weeks ago what I found was a weak inducer motor that when the burners light up would cause the pressure switch to open briefly but never did get an error code just kept trying to relight without locking out

  3. #29
    Join Date
    Nov 2007
    Location
    Mississippi
    Posts
    1,401
    I've had a goodman do the exact same thing to me as post #28.

  4. #30
    Join Date
    Jan 2011
    Location
    Ottawa, Canada
    Posts
    398
    Quote Originally Posted by tkhvacguy View Post
    I had a older Lennox unit doing the same thing a couple weeks ago what I found was a weak inducer motor that when the burners light up would cause the pressure switch to open briefly but never did get an error code just kept trying to relight without locking out
    I had one do this to me too. I cleaned everything and left it working and tested x5 and the next day the on-call guy (seasoned tech) found the p/s fluttering.

    how did you find out it was a weak inducer? pressure draw?

    Sent from my BlackBerry Runtime for Android Apps using Tapatalk 2

  5. #31
    Join Date
    Jan 2007
    Location
    N.E. Ok.
    Posts
    1,376
    Quote Originally Posted by stay gold jonny View Post
    What is the tool you have, and where can it be purchased?
    Probably talking about a molex pin extractor, Radio Shack or google.

  6. #32
    Join Date
    Oct 2011
    Location
    Toronto
    Posts
    35
    You could have a crack in the porcelain around the flame sensor that once heated expands and grounds out

  7. #33
    Join Date
    Sep 2010
    Location
    Gering, NE
    Posts
    14
    Quote Originally Posted by DeHeatify View Post
    I had one do this to me too. I cleaned everything and left it working and tested x5 and the next day the on-call guy (seasoned tech) found the p/s fluttering.

    how did you find out it was a weak inducer? pressure draw?

    Sent from my BlackBerry Runtime for Android Apps using Tapatalk 2
    Yes used my manometer to get the pressure draw on the pressure switch

  8. #34
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,121
    Quote Originally Posted by captube View Post
    Probably talking about a molex pin extractor, Radio Shack or google.
    Correct! we have a great little electronics supply house, not far from me that has everything, you could build the space shuttle with all that's in that store. I buy all my solderless terminals and etc. in there, they have bigger bulk packages and cost less than my supply house.

    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  9. #35
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,121
    Quote Originally Posted by GastecD View Post
    You could have a crack in the porcelain around the flame sensor that once heated expands and grounds out
    Could you eloborate a little on how this would happen? Thanks!
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  10. #36
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,121
    Quote Originally Posted by tkhvacguy View Post
    I had a older Lennox unit doing the same thing a couple weeks ago what I found was a weak inducer motor that when the burners light up would cause the pressure switch to open briefly but never did get an error code just kept trying to relight without locking out
    This is why you carry plenty jumpers, you jump one safety at a time till you find the issue. I always check/jump all the safety's first then once they are ruled out I move on.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  11. #37
    Join Date
    Sep 2011
    Posts
    85
    you can check your ground by checking continuity between neutral and ground. Ground and neutral are electrically connected (bonded) inside the breaker box. though i don't know if the unit cares about earth ground or just ground as a reference. carrier support told me that their units need a good earth ground even if ground reference is good. don't ask me why.
    Last edited by wdshea; 01-09-2013 at 06:32 PM. Reason: sorry, didn't realize this post was 3 pages...

  12. #38
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,121
    Quote Originally Posted by wdshea View Post
    you can check your ground by checking continuity between neutral and ground.
    Exactly! this is why I mentioned to check from the neutrals on the board to a cabinet ground, if I suspect an issue, I always jumper from the neutral/neutrals on the board to the cabinet ground.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  13. #39
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    19,506
    The process of ground checking in this situation is to eliminate any high resistance points between the board/module and the burners. The burners are the negative side of the rectification circuit, and the flame sense rod is the positive side. The board or module supplies an AC voltage to the sensor rod, referenced to the burner ground, and then it looks for the DC microamp current, as a result of the flame rectification.

    You MUST have a good connection between the burners and the ground connection on the board or module. In rooftop units, you can apply a jumper from the burner array to the module, and if the problem goes away, you know you have a ground connection issue.
    [Avatar photo from a Florida training accident. Everyone walked away.]
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