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Thread: Ducane burner, perhaps pilot, won't light

  1. #1
    DIY Junior Member bob12's Avatar
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    Unhappy Ducane burner, perhaps pilot, won't light

    Hello. Here are the main particulars on my Ducane furnace:

    • Natural Gas
    • Unknown model (80 efficiency)
    • 9 or more years old
    • Honeywell digital thermostat

    Furnace was working yesterday, but today it isn't. The sequence of how the furnace normally operates is as follows: motor (not blower) starts, burner lights, blower starts, hot air blows through registers. Now only the motor starts when a call for heat is sent. Earlier there was the sound of a motor not being able to turn, so I immediately shut off the furnace at the thermostat. Now the motor starts and turns when a call for heat is sent, and after it detects either the pilot and burner, or just the burner, won't light, it stops. I left the thermostat set to Heat, and it just cycles through trying to start the pilot and or burner. Blower will run if I set it to continuously run at the thermostat. I can't see much of what is going on inside without taking off any panels, which I haven't yet done. What I can see, through some vents, is a green blinking light lit. When the furnace is NOT trying to start it blinks three times, pauses, and blinks three times. When it TRIES to start the furnace the green light blinks continuously. The only other thing I'd add that may be relevant is that this particular unit has a condensate pump, and there is about 5 inches of water from where the hose for the pump connects to the pump. I don't hear it trying to pump out anything, and don't know if it's supposed to run when running the heat.

    Thanks!

    PS - Since I don't have any info on the model, please let me know where I can try and find out which model it is. Thanks.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    It sounds like it is either not actually firing, or if it is, it isn't detecting the flame. You need to take a panel off and get the exact model number, then you'll have a chance of figuring out what it really needs. But, from what you've said, it seems that it is not lighting or detecting the flame, and goes into a recycle, then tries again.

    Depending on the unit, they sometimes have vacuum pressure switches that detect proper air movement. If there's snow or some other obstruction preventing needed airflow, the safety interlock(s) will prevent it from firing. Inside of the cover there's almost always a wiring diagram. Now, understanding it isn't a given...some are a pain with proprietary symbols, and are like trying to read a foreign language. But, that may be your best hope until you can get a user's manual with more detailed help.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Junior Member bob12's Avatar
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    Jim,

    Thank you for the reply. Yes, that is exactly what it seems to be doing - continuously going into a recycle after not lighting or detecting the flame. (I can tell when it ignites, which it definitely isn't doing.) I will look to see if I can determine the exact model number, and report it back. If the system does have a vacuum pressure switch then how does the system attempt to detect proper air movement?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    A vacuum switch is just that, when a fan turns on, it creates a vacuum as air moves, which in the switch causes a small diaphragm to activate a switch. If it has one, it will show up in the wiring diagram.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    In the Trades Tom Sawyer's Avatar
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    Quote Originally Posted by jadnashua View Post
    A vacuum switch is just that, when a fan turns on, it creates a vacuum as air moves, which in the switch causes a small diaphragm to activate a switch. If it has one, it will show up in the wiring diagram.
    The blinking green light is your error codes
    If the condensate pump ain't working it won't let the furnace start
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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