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    blkjagg's Avatar
    blkjagg Posts: 25, Reputation: 1
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    #1

    Dec 31, 2008, 04:30 PM
    Start up sequence on furnace is sporadic.
    There are times when my Gas furnace Nordyne/Miller G3RA will do everything correct until it's time to introduce gas for ignition. The chamber motor starts, the glow plug lights I even hear the gas valve click open. The problem is sometimes it will immediately click closed.This may happen several times in succession until it eventually stays open (GAS VALVE) or the furnace stops trying and all you have is cold house and a running chamber motor.To make things even more interesting I've observed the glow plug light after the furnace had ignited.(This doesn't usually happen)
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert
    		  
    #2

    Dec 31, 2008, 05:34 PM
    What? Read this post


    https://www.askmehelpdesk.com/heatin...ml#post1455477
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #3

    Dec 31, 2008, 05:47 PM
    Try cleaning the flame sensor.
    Attached Images
     
    blkjagg's Avatar
    blkjagg Posts: 25, Reputation: 1
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    #4

    Dec 31, 2008, 06:35 PM

    First try still a little shaky... hesitated once or twice but did start. Replace it? Does this item fail often.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #5

    Dec 31, 2008, 06:43 PM
    The flame sensor usually does not fail BUt it does get dirty. If it makes you feel better replace it.
    blkjagg's Avatar
    blkjagg Posts: 25, Reputation: 1
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    #6

    Jan 1, 2009, 09:35 PM

    Cleaned flame sensor w/emery cloth. Problem still exists. If I turn furnace off and back on it may operate correctly.There have also been times when I've done that procedure over and over 5 or more times brfore it ignites. I also noticed glow plug turn back on after furnace ignited. Any suggestions would be greatly appreciated.
    KC13's Avatar
    KC13 Posts: 2,556, Reputation: 99
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    #7

    Jan 1, 2009, 09:44 PM
    A faulty pressure switch can produce this situation (doesn't support current when gas control is powered).Try this: remove C and NO wires from pressure switch, start unit, and jump wires together. See if unit runs normally, but only do this to test for faulty pressure switch. The ignitor is in the fire stream, and after several seconds the heat built up in the element can result in a glow, giving the appearance that it has been powered again.
    MarkwithaK's Avatar
    MarkwithaK Posts: 955, Reputation: 107
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    #8

    Jan 1, 2009, 10:02 PM

    The flame sensor will not be a factor unless you actually get ignition. Do you have an electrical meter? Can you test across the pressure switch and/or the coil on the gas valve?
    blkjagg's Avatar
    blkjagg Posts: 25, Reputation: 1
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    #9

    Jan 2, 2009, 12:41 AM

    Thank you for the advice... I am not getting any ignition when it fails. Everything works fine until it's time to introduce the gas. I tested the pressure switch as suggested and it is working correctly. I do have a meter... How do I test the gas valve?
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #10

    Jan 2, 2009, 03:00 AM
    Put the meter on the AC scale and hook up the meter to the gas valve power wires that you have removed from the gas valve. Turn on furnace and wait to see if any voltage registers on the meter. You will need to watch the meter carefully since the gas valve voltage will drop out on the safety.

    If you have the UTEC control board you might also try and remove and replace the 6 pin plug up near the HUM and EAC terminals since that has been proven to be a weak spot for electrical transfer on this circuit board and this plug also carry's power to the gas valve. This could explain the intermittent nature of your problem.
    See attachment below.
    Attached Images
  1. File Type: pdf 703799a.pdf (20.1 KB, 987 views)
    2. blkjagg's Avatar
    blkjagg Posts: 25, Reputation: 1
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    #11

    Jan 2, 2009, 12:29 PM

    House is warm again!! All of your assistance helped me eliminate everything with the exeption of the gas valve and the ignition control modual. Replaced ignition modual and furnace is working as intended. Family and I are very thankful.
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
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    #12

    Jan 2, 2009, 02:42 PM
    Glad you finally got the furnace working.
    MarkwithaK's Avatar
    MarkwithaK Posts: 955, Reputation: 107
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    #13

    Jan 2, 2009, 05:57 PM

    Good to hear, congrats.
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