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  1. #1

    Question Help with Lennox gas furnace

    Need help troubleshooting my Lennox G23 furnace. When on Auto it starts up, pilots ignite but as soon as it heats up getting ready to turn the blower fan on it shuts completly down, even our digital thermostat goes completly blank like the battery is dead. (which we replaced so it is new) We can get it to run by doing this: reset the thermostat or flip the power switch on the furnace, turn on the heat on auto, once it gets to the point its about to kick the blower motor on we turn the fan to "on". Troubleshooting so far has consisted of: cleaned ignitor, new thermostat battery, took the red wire and white wire on the thermostat and hooked together but still shuts off when blower gets ready to come on, checked that there was no loose wires. Please anyone have any ideas?

  2. #2
    Join Date
    Apr 2010
    Location
    Winnipeg,Manitoba,Canada
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    could be a few things.


    if this doesn't work. i came across others where the building was in a bad negative and the inducer blower motor could not overcome the negative pressure
    Last edited by beenthere; 12-01-2010 at 05:25 PM. Reason: removed DIy diagnostic check list

  3. #3
    Join Date
    Apr 2004
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    MN
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    It could be many different things. Most likely the control board/blower timing. However, this is not a fix that you want to guess on. These boards are expensive and cannot be returned once opened. Do yourself a favor and call a reputable service company.
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
    Gene Castagnetti-Director of the National Memorial Cemetery of the Pacific in Hawaii

  4. #4
    Join Date
    Apr 2010
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    Red Deer, Alberta
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    Quote Originally Posted by missy315 View Post
    We can get it to run by doing this: reset the thermostat or flip the power switch on the furnace, turn on the heat on auto, once it gets to the point its about to kick the blower motor on we turn the fan to "on".
    Since the furnace works fine when you turn the blower fan on manually, there could be a problem with the thermostatic switch that turns on the blower when temperature gets high enough. The reason everything is shutting off is for safety, the high limit safety (temperature too high) opens off all the control power and the gas shuts off. If there is not something simple that you can fix easily, please call a pro, the safety features are not to be trifled with.

    We had 2 home explosions here in Edmonton this year, one was a DIY gas furnace fellow who thought he had the "right stuff" and subsequently removed himself from the gene pool...

  5. #5
    Join Date
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    Quote Originally Posted by enb54 View Post
    Since the furnace works fine when you turn the blower fan on manually, there could be a problem with the thermostatic switch that turns on the blower when temperature gets high enough. The reason everything is shutting off is for safety, the high limit safety (temperature too high) opens off all the control power and the gas shuts off. If there is not something simple that you can fix easily, please call a pro, the safety features are not to be trifled with.

    We had 2 home explosions here in Edmonton this year, one was a DIY gas furnace fellow who thought he had the "right stuff" and subsequently removed himself from the gene pool...
    A good thought, but the G23 uses a timer in the circuit board to turn on the blower instead of temperature.
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
    Gene Castagnetti-Director of the National Memorial Cemetery of the Pacific in Hawaii

  6. #6
    We had the ignition control box replaced in Feb 2010, just noticed they put on a Honeywell brand---could this make a difference?

  7. #7
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    Apr 2004
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    The brand shouldn't make much of a difference, provided it is the correct replacement board and was installed/wired correctly. There is another circuit board (I think) in the blower compartment that actually controls blower operation.
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
    Gene Castagnetti-Director of the National Memorial Cemetery of the Pacific in Hawaii

  8. #8
    Ok thanks everyone my husband is checking everything everyone has posted. I will let you know!!

  9. #9
    Ok guys how can we tell if our limit switch is bad?

  10. #10
    Join Date
    Apr 2004
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    MN
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    At this point, I can only refer you to the site rules. Do it yourself advice is not allowed on this site. You are dealing with a safety control and do not know what you are doing. Call a pro.
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
    Gene Castagnetti-Director of the National Memorial Cemetery of the Pacific in Hawaii

  11. #11
    Join Date
    Apr 2010
    Location
    Red Deer, Alberta
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    653
    Quote Originally Posted by doc havoc View Post
    The brand shouldn't make much of a difference, provided it is the correct replacement board and was installed/wired correctly. There is another circuit board (I think) in the blower compartment that actually controls blower operation.
    You are correct, the G23 has a circuit board in the blower compartment, and blower is timer initiated, not via temperature. If down to this please get a pro in to check this out, circuit board repair is a manufacturer task, after field replacement.

    The other one of those natural gas explosions here took out most of a whole city block (that was a homicide case though)...

  12. #12
    Join Date
    Mar 2005
    Location
    burlington county n.j.
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    Quote Originally Posted by missy315 View Post
    We had the ignition control box replaced in Feb 2010, just noticed they put on a Honeywell brand---could this make a difference?
    Honeywell is the Lennox replacement for that furnace and not related to todays problem.

    call your contractor and tell him what its doing, only one thing can cause it on that furnace and i carry 2 of them in my truck.

  13. #13
    Join Date
    Jan 2004
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    Lancaster PA
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    Quote Originally Posted by missy315 View Post
    Ok guys how can we tell if our limit switch is bad?

    By calling a local HVAC service company. And having them come out.


    Sorry, this is not a DIY site.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

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