Pilot light won't stay lit. New thermocouple, clean orifice....Please Help.

Discussion in 'Heating / Cooling Systems' started by bowler001, Aug 20, 2009.

  1. bowler001

    bowler001 New Member

    Likes Received:
    Aug 6, 2009
    Howdy! First post and hopefully my only one needing help. :)

    Recently purchased an 85 starcraft with a duo-therm furnace. The blower works good when i do the operational check, and the pilot lights, but it just wont stay lit. It has a brand new thermocouple (didnt even have one when we got it), and I also removed the gas line for the pilot and cleaned it out, as well as the outlet on the valve. Stove works all 3 burners and is bright blue. Not sure what else to check. Any input would be great. Thanks!
  2. Zoltar

    Zoltar New Member

    Likes Received:
    Jun 2, 2009
    First, you wrote that you "removed the gas line for the pilot and cleaned it out."
    Did you take the pilot assembly completely apart and clean the orifice and pilot burner,
    or just blow out the 1/4" aluminum pilot line?
    The pilot assembly needs to be taken apart and completely cleaned, including the pilot orifice.

    Then when you replaced the thermocouple, where it screws into the gas valve,
    did you over tighten it ?
    Too tight and the thermocouple will short out the milivoltage that
    thermocouple produces when heated. Look at the end that screws into the gas valve.
    you will notice that the copper outer cover is insulated from the very end by a fiber disk.
    Too tight and you will flatten out that disk and short out the t-couple.
    You just need to make it finger tight, then use a wrench to give it -maybe- a 1/4 turn more.

    Then the pilot flame should be hitting the thermocouple about a 1/4" from the very tip of the t-couple.

    If you do all of that and you have a good flame on the thermocouple and the pilot goes out as soon as you release
    the knob on the gas valve, you just may need a new gas valve as well.

    As a side note: I worked in the service department at Duo-Therm in La Grange, Ind. in the late 70's.
    The 650 series furnace just went out of production and the 659 series furnace was new.

    Ahhh, the memories.... down town La Grange, one stop light for the whole county located downtown,
    the Amish buggy's and Corn School..... :)

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