Lennox Intermit. pilot
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  1. #1
    Join Date
    Mar 2005
    Posts
    24

    Confused

    Ok, first I will say hi to everyone being my first post.

    Next, I received an emergency call today. When I got there and turned the power back on the furnace, Lennox - MD#G23Q2\3-75-2, the ID motor kicks on. Does the usual venting, then sends 24V to the pilot and ignitor, now here is where we get tricky... ignitor is sparking like a champ but the pilot won't lite. My first thought was no gas, not the case, I lite it with a Bic Stick. Furnace burners kick on and away she goes. So I go upstairs and turn the Stat down. Walk back down the stairs and of course the furnace is going through the normal shut down procedure. Instead of going upstairs again I jumper R + W, again the pilot won't light so I use the Bic. This time I pulled the flame sensor as I have narrowed the problem to the pilot igniting. The pilot lights up with the Bic and now I have an approx. 8" bright orange flame going to the middle HX opening... Now I'm lost... I was thinking maybe a crack in the HX because my thoughts were back to the basics of:

    Blue flame = normal
    Orange/yellow = Too much Oxygen
    White = Not enough Oxygen

    Then I had someone tell me that I have Orange and White mixed up! Can someone verify that and maybe shed some light on this damn pilot?? Oh, I replaced the gas valve just to be safe with one I had on the van and pilot does the same thing... Thanks for any input!

  2. #2
    Join Date
    Feb 2005
    Location
    Kentucky
    Posts
    57
    Is the pilot orfice and line cleen, I have seen on the g23 that the blue ignition control get week and did not put out enough spark to light the pilot. Replaced the ignition control and took care of problem. Also is the sensor ok.

  3. #3
    Join Date
    Mar 2005
    Posts
    24
    Pilot and orifice line is clean, I pulled and cleaned as I checked the spark. I am getting 30v on the ignition and the sensor works great. I'm just mind boggled on that darn 8" flame from the pilot.... It is being sucked into the HX by the Inducer motor... checked the amp draw and I get 1.0 on both lines motor reads 1.5 on the label...

  4. #4
    Join Date
    Feb 2005
    Location
    Kentucky
    Posts
    57
    The only way I could see a 8 inch pilot on a lennox g23 would be no orfice or wrong orfice in pilot or pilot adj on gas valve not set correct.

  5. #5
    does burner flame turn yellow when blower comes on.

  6. #6
    Join Date
    Mar 2005
    Posts
    24
    Just the middle one stays yellow... That is what led me to believe the middle HX was cracked... Then I get this other guy saying I have the colors from the basics mixed up:

    Blue = Normal
    Yellow/Orange = Too much Ox = crack in exchanger
    White = Not enough Ox

    I thought those above are the right combo, am I wrong? If I am then why the heck does a camp fire burn yellow/orange? Should burn white according to him.. lol. Regardless I say crack. Anyone else? Gonna open the plenum tomorrow morning...

  7. #7
    sounds like pilot valve on gas valve is having problems.cracked hx usually burner flame turns yellow or rollout occurs with cracked hx.

  8. #8
    Join Date
    Feb 2005
    Location
    Kentucky
    Posts
    57
    It sounds like there is more problems than a cracked heat exchanger. One way you could check to see if you have a crack on that furnace is pull the blower. That furnace has had problems with heat exchanger, it drops little rings in blower about the size of dime that is were they hold heat exchaner together and pops apart. also is the pilot 8 inches without indoor motor running.

  9. #9
    Join Date
    Mar 2005
    Posts
    24
    Originally posted by hot wired
    sounds like pilot valve on gas valve is having problems.cracked hx usually burner flame turns yellow or rollout occurs with cracked hx.
    New valve was installed, I checked the gas pressure = 3.5" W.C., and the flame is yellow/orange - 8" long - and it does roll. I just got thrown when another Tech reversed the colors on me... he is older and has, well thought had, more years in the field for exp. So he kinda made me second guess myself. Judging from the replies, I am right about the colors. And if I don't find a crack in that middle HX tomorrow I will definately be bamboozled! Never seen one like this before.

  10. #10
    Join Date
    Mar 2005
    Posts
    24
    Originally posted by pipefitter2005
    It sounds like there is more problems than a cracked heat exchanger. One way you could check to see if you have a crack on that furnace is pull the blower. That furnace has had problems with heat exchanger, it drops little rings in blower about the size of dime that is were they hold heat exchaner together and pops apart. also is the pilot 8 inches without indoor motor running.
    pilot is 8" with Inducer running only and same with blower running.

  11. #11
    Join Date
    Feb 2005
    Location
    Kentucky
    Posts
    57
    regardless of colors you should not have a 8 inch pilot and should not have to light it with bic lighter.

  12. #12
    Join Date
    Mar 2005
    Posts
    24
    *laughs

    Yes, I know this. Just never seen it before and wondered if anyone else had. Also wondered about the color thing... kinda threw me for a loop when he said it was opposite. Thanks for the quick replies all! I think I will stick around and learn from some of the vet's.. and who know's might even pick something up from someone new to the job...

  13. #13
    Join Date
    Jul 2002
    Location
    St Paul, Minnesota
    Posts
    3,468
    Is the sensor wire touching anything like the pilot tube? Are the spade connects good? Blue Johnson control? Nat gas or propane stamped on oriface?

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