Lennox G20 - Ignition Problem, clicks and sometimes ignites
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  1. #1
    For the past few weeks I've noticed that my heating system doesn't turn on. I've traced it back to the ignition system not lighting.

    Sometimes it just sits and clicks, then shuts off. I have to reset the system to start again, eventually it will light.

    Also, it seems that it turns off before it reaches it's target temp alot.

    I read a fix for the ignition problem could be:
    The ignitor has a thick Gray(or Blue) tube-like wire going straight to the control circuit board to a one inch round device. Pull it off, trim 1/4" to 1/2" off and push/turn it back on.

    As for the furnace stopping before it's target temp, could that be the flame sensor?

    Thanks for your responces...

  2. #2
    gasman Guest
    can not help without knowing more. is it spark ignition pilot? or mercury switch pilot? also furnace shutting off before desired temp would be in your thermostat. if round Honeywell t-stat. check if it is level and check the heat anticipator. Ted.

  3. #3
    Join Date
    Feb 2004
    Location
    chicago suburbs
    Posts
    4,422
    what about the limit switch, Ted
    FILL OUT YOUR PROFILE!!

  4. #4
    gasman Guest
    yes tinner73 that is another possibility if filter is blocked. Ted.

  5. #5
    Join Date
    Oct 2003
    Location
    west chester pa
    Posts
    343
    replace the blue ignition control with lennox part 53l90. control is known for erratic lock outs due to poor solder connections internal to board. kit also comes with new flamesensor.

  6. #6
    Join Date
    Dec 2004
    Posts
    441
    Is this the first G20 you have ever worked on?

  7. #7
    Replace the blue ignition control(Johnson Control) with lennox part 53l90. This is a Honeywell part with new flame sensor, heat shield and a few wire nuts and screws. There is a simple wire change required.

  8. #8
    Join Date
    Nov 2004
    Location
    CA
    Posts
    238
    Yes, as mentioned above 53L90 is due. Simple, there is one new wire from flame sensor to ign. module.
    while you are at it, and ONLY if you are an HVAC tech., check and clean the aluminum pilot tubing.

  9. #9
    Join Date
    Jun 2004
    Location
    Orange County California
    Posts
    63
    Doubleshot - You stated:
    “For the past few weeks I've noticed that my heating system doesn't turn on. I've traced it back to the ignition system not lighting. Sometimes it just sits and clicks, then shuts off. I have to reset the system to start again, eventually it will light.”

    If upon visual inspection you find that the HSI glows, the gas ignites (meaning the heater comes on temporally) then cycles off and you continue to hear a clicking sound. You most likely have a bad Flame Sensor.

    Here is how it works. The thermostat calls for heat. The Ignition Module sends 120V to the HSI. You hear a clicking sound. The gas valve opens which releases the gas over the HSI and your furnace ignites. The Flame sensor recognizes that a flame is present and sends a signal back to the Ignition module and the audio clicking stops. If however the flame sensor is bad it will continue to click until the module cycles off.

    Anyway you can either replace the Flame Sensor or the entire ignition system that includes the sensor as suggested by pipedope and energy-wise on previous posts. The choice is clearly yours.



    [Edited by rcrainman on 02-28-2005 at 08:52 AM]

  10. #10
    gasman Guest
    in my experience, just cleaning the flame rod with emery cloth and checking the microamps usually does the trick.

  11. #11
    Thanks you guys, I fixed the ignition problem with it not igniting. The wire that ran to the ignitor needed to be trimmed then I twisted it back on and it ignites without any problems now...

    Sometimes however it doesn't stay on still, and I suspect it's the flame sensor, but since it works most of the time now, I am suspecting it just needs a good cleaning and should all work fine.

    Thanks again for all your help!

  12. #12
    Join Date
    Oct 2003
    Location
    west chester pa
    Posts
    343
    Originally posted by rcrainman
    Doubleshot - You stated:
    “For the past few weeks I've noticed that my heating system doesn't turn on. I've traced it back to the ignition system not lighting. Sometimes it just sits and clicks, then shuts off. I have to reset the system to start again, eventually it will light.”

    If upon visual inspection you find that the HSI glows, the gas ignites (meaning the heater comes on temporally) then cycles off and you continue to hear a clicking sound. You most likely have a bad Flame Sensor.

    Here is how it works. The thermostat calls for heat. The Ignition Module sends 120V to the HSI. You hear a clicking sound. The gas valve opens which releases the gas over the HSI and your furnace ignites. The Flame sensor recognizes that a flame is present and sends a signal back to the Ignition module and the audio clicking stops. If however the flame sensor is bad it will continue to click until the module cycles off.

    Anyway you can either replace the Flame Sensor or the entire ignition system that includes the sensor as suggested by pipedope and energy-wise on previous posts. The choice is clearly yours.



    [Edited by rcrainman on 02-28-2005 at 08:52 AM]
    The lennox g20 is spark ignition!!!!!!!!

  13. #13
    Join Date
    Oct 2003
    Location
    west chester pa
    Posts
    343

    Thumbs down

    [QUOTE]Originally posted by doubleshot
    [B]Thanks you guys, I fixed the ignition problem with it not igniting. The wire that ran to the ignitor needed to be trimmed then I twisted it back on and it ignites without any problems now...
    I bet you didn't.

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