Furnace thermocouple keeps going bad

Discussion in 'Home Repair' started by mdw7, Nov 10, 2003.

  1. mdw7

    mdw7 Guest

    Hi,
    I have a chronic problem with my home furnace. Too often, the pilot
    light goes out. Sometimes I can relight it, but after a few weeks, it
    becomes impossible to relight. If I change the thermocouple, it works
    fine for a few weeks, then the problem returns. What is causing the
    thermocouples to go bad?
    Thanks!
    Matt
    mdw7, Nov 10, 2003
    #1
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  2. mdw7

    My name Guest

    One thing that I have learned ( Family owns 25 rental units) is that these
    thermocouples can more often than not be recycled.

    Try this next time: using a scotch brite pad, scuff the surface. Also, the
    blue tip of the flame (assuming it is a standing pilot) should be pointed
    at the mid section of the TC.

    How old is the furnace?

    larry

    (mdw7) wrote in
    news::

    > Hi,
    > I have a chronic problem with my home furnace. Too often, the pilot
    > light goes out. Sometimes I can relight it, but after a few weeks, it
    > becomes impossible to relight. If I change the thermocouple, it works
    > fine for a few weeks, then the problem returns. What is causing the
    > thermocouples to go bad?
    > Thanks!
    > Matt
    >
    My name, Nov 10, 2003
    #2
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  3. Can you hold it up to the monitor? I can't quite picture that.

    --

    Christopher a. Young
    Learn more about Jesus
    www.lds.org
    www.mormons.org


    "mdw7" <> wrote in message
    news:...
    Hi,
    I have a chronic problem with my home furnace. Too often, the pilot
    light goes out. Sometimes I can relight it, but after a few weeks, it
    becomes impossible to relight. If I change the thermocouple, it works
    fine for a few weeks, then the problem returns. What is causing the
    thermocouples to go bad?
    Thanks!
    Matt
    Stormin Mormonn, Nov 10, 2003
    #3
  4. mdw7

    CBHvac Guest

    "mdw7" <> wrote in message
    news:...
    > Hi,
    > I have a chronic problem with my home furnace. Too often, the pilot
    > light goes out. Sometimes I can relight it, but after a few weeks, it
    > becomes impossible to relight. If I change the thermocouple, it works
    > fine for a few weeks, then the problem returns. What is causing the
    > thermocouples to go bad?
    > Thanks!
    > Matt


    First.
    Sanding the thermocouple is a waste of time. IF the units in the flame good,
    the heats going to be transfered and will work.
    If its not covered in white ash, then sanding is a waste of time...did I say
    that sanding is a waste of time?

    Second.

    Thermocouples come in many qualitys...really. Honeywell is not always the
    best in this case...however, you are not going to get a quality TC for $5 at
    Lowes.
    The ones we sell are $25 wholesale and we get ZERO failures thus far.

    Third.

    Installation.
    If the units been dropped, or mangled and someones bent it at crazy angles
    to try to get it in place, its going to fail sooner, than later.
    Also, the flame for the unit does NOT need to cover the entire unit....just
    the tip....say..1/3 or less of the unit...any more, and its going to fail.
    CBHvac, Nov 11, 2003
    #4
  5. mdw7

    M R Guest

    Stormin Moron wrote:
    >



    <ahh...>
    M R, Nov 11, 2003
    #5
  6. mdw7

    TURTLE Guest

    "mdw7" <> wrote in message
    news:...
    > Hi,
    > I have a chronic problem with my home furnace. Too often, the pilot
    > light goes out. Sometimes I can relight it, but after a few weeks, it
    > becomes impossible to relight. If I change the thermocouple, it works
    > fine for a few weeks, then the problem returns. What is causing the
    > thermocouples to go bad?
    > Thanks!
    > Matt


    This is Turtle.

    Like CBHVAC said I think you have one of these two problems.

    1) your buying cheap thermocouples at Home Cheap-0 and they are failing
    like they are suppose to.

    2) Your heating up the middle to the bottom of the thermocouple head and
    it will burn it up. The flames should not hit nothing but the top 1/3 of the
    thermocouple head to work properly. If you heat the bottom half of the
    thermocouple head. you will get a negitive 24 mill-volts. If you heat the
    top half of the thermocouple head you will get a possitive 24 mill-volts. If
    you heat the middle of the thermocouple head. you will get a + positive 24
    mill-volt and a negitive 24 mill-volts which equals zero mill-volts but then
    in about a week it will burn up completely.

    So back to statement # 1 : heat only the top 1/3 of the thermocouple head
    and use a hvac thermocouples and not the hot water tank thermocouples. Home
    Cheap-0 does not sell hvac thermocouples and you will have to go to a hvac
    supply house or appliance parts house and get a hvac thermocouple [ used for
    gas hvac furnaces ] to use. The hvac thermocouple will run you $12.00 to
    $25.00 depending on length and brand. Hot water thermocouples put out about
    26 mill-volts and a hvac thermocouple will put out about 30 mill-volts. A
    thermocouple can loose as much as 1/2 a mill-volt per year of operation and
    will last 8 years longer than a hot water tank thermocouple.

    TURTLE
    TURTLE, Nov 11, 2003
    #6
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