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Thread: Lennox 80 UHG

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  1. #1
    Join Date
    Dec 2004
    Posts
    441
    Nothing really ticks me off more than working on junk all day long than stepping into my home shop and listening to this piece of c!?p light off and miss it's blower sequence according to a "Pressure Switch" anamoly! I've replaced everything but the combustion blower assy, removed the pressure switch orfice, and it still does it's thing! Can anyone reccommend something for replacing the Heatcraft board that makes sense? Or is there really a Lennox God out there that would admit there is a problem with this unit somewhere between the combustion blower and the pressure switch!

  2. #2
    Join Date
    Dec 2004
    Posts
    441
    What can be more degrading than having a tech buy his own companys equipment? The acknowledgement that it's junk or the fact that there is no factory support?

  3. #3
    Join Date
    Nov 2004
    Location
    CA
    Posts
    238
    explain with more details what is happening. Does the Pressure switch make the contacts ? Did you measure the Negative pressure the Ventor is pulling ? To do this: get a barbed "T" fitting and some 1/4" plastic hoses and hook it up between Ventor and P.S.

    Also, check the damn Ventor for proper Amps. If the furnace is using Nitride ignitor - replace the damn thing - it messes everything in the sequence.

    Come back with more info - will try to help.

  4. #4
    Join Date
    Dec 2004
    Posts
    441
    Lennox undersized the combustion blower on this unit, it has the smallest rated pressure switch of all units .26.

  5. #5
    Join Date
    Nov 2004
    Location
    CA
    Posts
    238
    Indian, at .26"w.c. the darn thing should make the contacts without a hesitation. O.K. do that - pull the 1/4" hose and well ... pull the vacuum with your mouth. Use napkin or some thick paper - because some say one could catch Legionere disease by suckin in the air from the hose.
    That should eliminate some questions.

  6. #6
    Join Date
    Dec 2004
    Posts
    441
    No one likes to go home and work on the problems they deal with all day, point well taken, it's time to get all the facts, and then call tech support and lay it on the line.

  7. #7
    Join Date
    Jul 2002
    Location
    St Paul, Minnesota
    Posts
    3,468
    Does it have the original exhaust blower?
    A common change out. I have put a meter across the two terminals on the p.switch. Should be zero volts when the unit is running.....then the meter starts to read volts and immediately goes back to zero as the switch recloses. But that sudden opening of the switch is all the board needs to go into restart and after 3 of these, goes into lockout. Same type of problem as the 80mgf's sensor. Without the upgrade kit,you get lockouts on flame sense.

  8. #8
    Join Date
    May 2004
    Posts
    39
    PARTS CHANGER. Since you are good at replacing part after part. Might as well keep going to other part. Give us a step by step of problem you encounter so we can help man

  9. #9
    Join Date
    Dec 2004
    Posts
    441
    Originally posted by stef
    PARTS CHANGER. Since you are good at replacing part after part. Might as well keep going to other part. Give us a step by step of problem you encounter so we can help man
    I fix things that would make your little world swim backwards, After I'm done with my day the last thing I want to do is what I do for you. Hey, maybe you are right, If you can fix this in a one hour service call I would be more than willing to pay the one hour shop charge! Then maybe you youd earn the right to pack my tools!

  10. #10
    Join Date
    Dec 2004
    Posts
    441
    Originally posted by stef
    PARTS CHANGER. Since you are good at replacing part after part. Might as well keep going to other part. Give us a step by step of problem you encounter so we can help man
    Thank you for the insultations, Somehow this reminds me of daily business!

  11. #11
    Join Date
    Dec 2004
    Posts
    441
    I don't know if anyone else has noticed this before, but on this particular machine Lennox put the primary limit in series with the pressure switch. These units are similar to G24 units with exception to the primary limit. I have replaced several G24 combustion blowers and pressure switches due to this same problem with a "high altitude" kit that cured the problem. Has anyone heard of such a retro kit for the 80 UHG? Yes this was parts changing stef.

  12. #12
    Join Date
    Nov 2001
    Posts
    1,874
    With an attitude like that on here,
    you might as well get used to talk'n to your self.
    Like you have been.

    If your so up on lennox, then you know that they do have support.

    So keep chang'n things and maybe we all can some day carry your tool bag,

    But on the way in the house I'd probably stop by my truck and get my meter.
    If you try to fail, and succeed.
    Which have you done ?



  13. #13
    Join Date
    Jul 2002
    Location
    St Paul, Minnesota
    Posts
    3,468
    just the ones I mentioned; change out the pilot rod/sensor assembly and the exhaust blower. Ones with black paint were the early model I believe and failed often, just after warranty.

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