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Thread: Anyone know anything about gas furnaces?

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  1. #1
    Join Date
    Sep 2008
    Posts
    322
    It does get 24v to the valve, when it tries to light, something cuts the 24v and the gas cuts off. I do appreciate the help. Its given me lots of things to try.

    Something else. What happens if the intake for the furnace is too small? I think I just answered that, the furnace intake is 16x25, the actual hole for the intake is 8x25. Any thoughts on that? Its a 60k btu unit.
    - Waiting for an lq9 swap - Super 40 center in dual out - battery swap to spare tire location - exhaust turndown -

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  2. #2
    Join Date
    Dec 2005
    Location
    Chicago-ish
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    174
    How can you go this long without a furnace?
    After watching your video again, I am going back to my dirt answer.
    What you will notice with not enough return (intake) air is the flames will light normally and run for awhile. In anywhere from a couple to several minutes, the flames will shut off even though the thermostat isn't satisfied. The blower will remain running like it normally does after the flames shut off, except after a few minutes the ignition cycle will start again. It is normal for the blower to stop at the start of each ignition cycle, so that is not an indicator. The only way you can be sure that the thermostat has not reached setpoint when the flames go out is to test across the "R" and the "W" low voltage terminals. If your meter shows no voltage, the thermostat is still calling. If you have voltage from terminal to terminal, the thermostat is satisfied.
    There is a limit switch that senses the air temperature downstream of the burners. When the switch gets too hot because of a lack of airflow, it kills the burners and keeps the blower running until it cools off and the cycle starts again.
    If this is happening to your furnace, it is a seperate issue from what is happening in your video.
    2000 Sierra 2500 HD. 408 (11-2007) Whipplecharged, Big (18x24x4) FMIC.

  3. #3
    Join Date
    Sep 2008
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    322
    Quote Originally Posted by MikeGyver View Post
    How can you go this long without a furnace?
    After watching your video again, I am going back to my dirt answer.
    What you will notice with not enough return (intake) air is the flames will light normally and run for awhile. In anywhere from a couple to several minutes, the flames will shut off even though the thermostat isn't satisfied. The blower will remain running like it normally does after the flames shut off, except after a few minutes the ignition cycle will start again. It is normal for the blower to stop at the start of each ignition cycle, so that is not an indicator. The only way you can be sure that the thermostat has not reached setpoint when the flames go out is to test across the "R" and the "W" low voltage terminals. If your meter shows no voltage, the thermostat is still calling. If you have voltage from terminal to terminal, the thermostat is satisfied.
    There is a limit switch that senses the air temperature downstream of the burners. When the switch gets too hot because of a lack of airflow, it kills the burners and keeps the blower running until it cools off and the cycle starts again.
    If this is happening to your furnace, it is a seperate issue from what is happening in your video.
    It works, just takes it a few tries to get it to come on. No its not doing anything like that, only issue I know of is whats in the video. I'm agreeing on dust or dirt, I'll attack that in the morning, pulling out the burner and cleaning them.
    - Waiting for an lq9 swap - Super 40 center in dual out - battery swap to spare tire location - exhaust turndown -

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  4. #4
    Join Date
    Feb 2008
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    edmond, ok
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    299
    Hope cleaning works. Let us know if it does not.

    Also what state do you live in. I am guessing up north some where from the snow pics.
    07 GMC ccsb 1500 4x4, front replacment bumper, 285 70 r17 on 17" black helo max 6, Dual flowmasters dumped.

  5. #5
    Join Date
    Sep 2008
    Posts
    322
    Quote Originally Posted by hunt4game29 View Post
    Hope cleaning works. Let us know if it does not.

    Also what state do you live in. I am guessing up north some where from the snow pics.
    Yes it work beautifully! It had lots of dust caked in the tubes. But didn't really look like it could cause an issue. Put all back together, turned it on, and the first time the ignitor glowed the gas went through all three tubes and light without an issue. Washington state, but was the state of confusion with the furnace. Thanks for you help!
    - Waiting for an lq9 swap - Super 40 center in dual out - battery swap to spare tire location - exhaust turndown -

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