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  1. #1
    Join Date
    Feb 2012
    Posts
    9

    Gas Furnace problem -Old Lennox-

    -Hi all

    I'm having a problem with my old 28yr old Lennox.

    When the furnace runs it will run for about one to two minutes and then it will flame out,blower continues to run , it cools down and then it will re-fire.

    So I guess the unit is running too hot?

    To make a long story short a Tec came out,on the ticket he diagnosed it as a faulty gas valve,I replaced it and the problem still continues.
    I call the company back out and Tec # 2 says the controller was bad so I replaced it.
    The problem still continues.

    Wile watching the unit go through it cycle last night I decided to pull open the filter door ,the unit continues to run as normal ,the problem goes away and it never goes off on high limit.

    "The filter is new and there is nothing blocking the duct"

    So I'm thinking its the blower motor or the Capacitor.But The motor spins freely and does not get hot.The capacitor looks ok but I have no Idea yet on how to test it or if even the will cause the motor to run slower or if this is the problem at all.

    I'm so pissed with the company I don't want them back.

    Could someone be so kind to head me In right direction,your thoughts or suggestions would be greatly appreciated.

    Thanks
    -CW

  2. #2
    Join Date
    Feb 2008
    Location
    Altmar, New York, United States
    Posts
    4,362
    when was the last time it was serviced?

  3. #3
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,433
    IF, and that is quite a large IF, it is indeed cycling on high limit, random parts replacement will not resolve the problem.

    You need to correct the root cause which is probably related to the ductwork and not the furnace.

  4. #4
    Join Date
    Aug 2011
    Location
    Eastern Shore, MD
    Posts
    798
    Quote Originally Posted by jpsmith1cm View Post
    IF, and that is quite a large IF, it is indeed cycling on high limit, random parts replacement will not resolve the problem.

    You need to correct the root cause which is probably related to the ductwork and not the furnace.



    im sure it doesnt help that your system is 28 years old either

  5. #5
    Join Date
    Dec 2007
    Posts
    4,670
    did the "company" replace the parts or did you?
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
    from an excerpt by Paul Jacob in Sun City, AZ

  6. #6
    Join Date
    Feb 2012
    Posts
    9
    Snupytcb- It get serviced regularly .


    Jpsmith1cm- Are you saying the returns may need cleaning?They look ok.The duct work itself hasn't changed .I will pull the returns down and have a closer look.

    Gross - yes its old but its been very reliable up until now.I think a lot of Tecs today just don't know the older units.First thing they want to do of course is sell ya a new unit.
    The heat exchanger is still in great shape !

    Which one of the newer units have battle ship metal heat exchangers ? "Grin"

  7. #7
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,829
    I'm assuming this is a gas furnace and not oil? No specific equipment information doesn't give us much to lean on. Even a few pictures would at least tell us with what we're dealing. A good company should obtain the following information as they perform a thorough trouble shooting job. These won't necessarily mean anything to you but should to a good tech.

    RAT, SAT, RESP, SESP, TESP, CFM. This is information that is germane to both oil and gas units. For gas furnaces, inlet gas pressure in IWC, manifold pressure in IWC, total Btu input to the furnace by clocking the gas meter. The tech may find the problem without going through all those steps but if necessary, all steps should be taken.

    However, if the problem is NOT temperature related, then the possibilities are almost endless. I appreciate your frustration with the servicing company but please understand that not all techs are cracker jack aces and if the problem is beyond basic, it may take a senior tech to solve the problem. Now if THEY have been putting on the parts, I'd expect them to stand behind their work. Btu if YOU have been replacing the parts based on their opinion, then you've got no recourse for what's been done. It's difficult to determine who's on first by your description.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  8. #8
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    your unit may be border line on return
    what type filter are you useing if 3m then pull it and put in a cheap one

    the evape coil may also be plugged and need a good cleaning
    age IMHO isnt your issue
    something has changed and needs to be found if in fact it is over heating and not something else causing your problem

    what ever you do
    DO NOT LEAVE THE BLOWER DOOR OFF OR YOU COLUD DIE

  9. #9
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,433
    Quote Originally Posted by CWloop View Post
    Snupytcb- It get serviced regularly .


    Jpsmith1cm- Are you saying the returns may need cleaning?They look ok.The duct work itself hasn't changed .I will pull the returns down and have a closer look.

    Gross - yes its old but its been very reliable up until now.I think a lot of Tecs today just don't know the older units.First thing they want to do of course is sell ya a new unit.
    The heat exchanger is still in great shape !

    Which one of the newer units have battle ship metal heat exchangers ? "Grin"
    Actually, I'm referring to a potential airflow problem.

    I cannot see the installation from here, but the symptoms that you describe MAY, and I must emphasize MAY be a low airflow problem.



    I'll turn your last question about on you. How many NEW units operate at typically 50-60% fuel efficiency?

  10. #10
    Join Date
    Feb 2012
    Posts
    9
    Quote Originally Posted by skippedover View Post
    I'm assuming this is a gas furnace and not oil? No specific equipment information doesn't give us much to lean on. Even a few pictures would at least tell us with what we're dealing. A good company should obtain the following information as they perform a thorough trouble shooting job. These won't necessarily mean anything to you but should to a good tech.

    RAT, SAT, RESP, SESP, TESP, CFM. This is information that is germane to both oil and gas units. For gas furnaces, inlet gas pressure in IWC, manifold pressure in IWC, total Btu input to the furnace by clocking the gas meter. The tech may find the problem without going through all those steps but if necessary, all steps should be taken.

    However, if the problem is NOT temperature related, then the possibilities are almost endless. I appreciate your frustration with the servicing company but please understand that not all techs are cracker jack aces and if the problem is beyond basic, it may take a senior tech to solve the problem. Now if THEY have been putting on the parts, I'd expect them to stand behind their work. Btu if YOU have been replacing the parts based on their opinion, then you've got no recourse for what's been done. It's difficult to determine who's on first by your description.

    Thank you for your response.

    The company I called charges bucks for a diagnostic to find the problem.My reason for me doing it this way was to save money on labor the company would have charged to replace the part or parts needed.

    I consider myself mechanically inclined enough to do the work.However I don't have the tools or knowledge to diagnose properly and didn't want to throw parts at it,even though thats what I wound up doing anyway and even payed extra

    The company didn't charge me for the second Tec visit, only the first time for the diagnosis.There was nothing wrong the the work I did,it was diagnosed wrong from the start.

    I wasn't home home when the first guy came out so I don know what he did .The second guy only had a multimeter and somehow determined the gas valve was bad which it was not.


    In a perfect world I think I could of saved some money,my intentions were good but I think got screwed in the end .

    BTW its a Lennox Gas Furnace ,the description is in the post title.I can post more info and pics if need be.

    Thank you for your reply
    -CW

  11. #11
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,433

  12. #12
    Join Date
    Feb 2012
    Posts
    9
    The filter door is on the return side not the supply side,the flow at the registers/vents still has good flow.

    I checked the fins on squirrel cage and there clean too.I have a cheap filter,fiberglass kind.

    Couple pix of the unit and the unnecessarily replaced parts.If The the A coil was clogged why does the unit operate normally with the filter door open?
    Attached Images Attached Images   

  13. #13
    Join Date
    Feb 2012
    Posts
    9
    Quote Originally Posted by jpsmith1cm View Post
    Actually, I'm referring to a potential airflow problem.

    I cannot see the installation from here, but the symptoms that you describe MAY, and I must emphasize MAY be a low airflow problem.



    I'll turn your last question about on you. How many NEW units operate at typically 50-60% fuel efficiency?

    Thank you for your opinion.


    Point well taken on your last question.
    I think the new units are great on efficiency.

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