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  1. #1
    Join Date
    May 2014
    Posts
    3

    Confused york 90% loosing flame signal weird problem

    Hey all this is my first time posting here so please excuse any mistakes I make. I have a friend that needed a new furnace and wanted a york 90% installed so we did that. It is a high altitude location running propane.( did install a high altitude switch and full propane conversion). It is an intermittent problem of loss of flame signal and locking out after so many trys.(code 7 i think don't have the book with me or my notes lol) I have been pulling my hair out over this one I have been getting a good flame signal and can't find anything apparently wrong with it, but I also work in the commercial world and focus mostly on chillers and controls so I was thinking surely someone here has more experience with this and has some suggestions. Here is a list of things that have been tried: cleaned/replaced flame sensor, new low gas cutout switch, new wiring, cleaned/new orifices, new gas valve, new control board, new ignitor for the hell of it, verified quality grounding, added a ground, checked/ changed polarity,verified and increased volume of gas to the unit(not gas pressure), verified correct gas pressure. verified combustion air(even errors with the front cover off sucking all the air it could want). I did talk to one guy who said it sounds like a plugged up secondary heat exchanger, does that sound right, if so could someone explain how it is, I am going to check it anyways. I am completely stumped and running out of ideas. So any ideas that you would have would be greatly appreciated, and don't hold back at this point there would be no such thing as a bad or stupid idea(hopefully it is stupid easy thing I am missing) so any help would be great thank you.

  2. #2
    Join Date
    Jun 2013
    Location
    Horton, MI
    Posts
    15
    You said the combustion air is drawing well from outside. Is there a chance its recirculating exhaust gas back into the furnace? This can for sure make you lose your flame.

  3. #3
    Join Date
    Jun 2013
    Location
    Horton, MI
    Posts
    15
    Sorry I see you had the front cover off to eliminate this possibility

  4. #4
    Join Date
    Jun 2013
    Location
    Horton, MI
    Posts
    15
    Years ago york had problems with condensate returning back on the exhaust pipe on the 90% furnaces. The fix was to put a wye and drain right at the furnace so any condensate would drain and not go through the furnace. Also if any exhaust piping is close to being level condensate can accumulate in the pipe and start sloshing after a while this will trip you pressure switch.

  5. #5
    Join Date
    May 2014
    Posts
    3
    good thought, I don't seem to be getting any excessive condensate in the combustion blower but I will check it again, I havn't ever seen the pressure switch open up or had it set a code for the combustion air. I will check all the lines and combustion blower anyways for condensate.

  6. #6
    Join Date
    May 2014
    Posts
    3
    Also my friend says it will do it on like the first call then if you reset the power it will be good the rest of the day, not sure if its a coincidence or if thats really happening

  7. #7
    Join Date
    Jan 2013
    Location
    Western Ky
    Posts
    150
    check your grounds ive had weak grounding cause wierd issues with flame sense

  8. #8
    Join Date
    Jan 2013
    Location
    Western Ky
    Posts
    150
    check all the way to panel

  9. #9
    timebuilder's Avatar
    timebuilder is offline AOP Committee/Professional Member*
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    17,816
    1) Some units need to see a good ground continuity to the panel to allow them to operate.

    2) That ground has nothing to do with flame sense.

    3) The burners must be "grounded," IE, connected to the common of the ignition control.

    4) Check the schematic diagram to see how the burners are connected so that proper rectification occurs. That connection is usually where the problem happens.
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  10. #10
    Join Date
    Jan 2009
    Location
    Middle of the Oregon Coast
    Posts
    193
    LP kit has a low gas pressure switch that is wired into the flame sensor. My first guess is that you have an intermittent LP regulator problem - not letting any gas through. The 3" nipple that you attached to the gas valve with the hole in the side, and the switch that you added to that? It's the one with the 2 purple wires.....


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