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  1. #1

    furnace ignites then after 10-25min cuts off

    Rookie tech working on a Sears brand furnace model 867.764221
    The furnace comes on and stays lit for 10-25 min then shuts off. has a spark ignition that is also combination with the flame sensor. Is it a dirty flame sensor with a combination of a failed spark box? Used my multi meter and also turned on furnace disconnected
    the flame/ignition sensor write and

  2. #2
    Join Date
    Feb 2008
    Location
    Altmar, New York, United States
    Posts
    5,177
    are you sure it is not tripping high limit? or even satisfing t=stat?

  3. #3
    Sounds like high limit like snupytcb said. Check airflow. Dirty blower wheel. Dirty filter or stopped up evap

  4. #4
    Join Date
    Apr 2008
    Location
    Greenwood Lake, ny
    Posts
    50
    you should check air flow,make sure its not shutting off on high limit.Also make sure that prving switch is not loosing its draft ,may have clogged tube on the inducer.

  5. #5
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,569
    Is this a condensing furnace? The drain could be clogged and backing up.

  6. #6
    Join Date
    Apr 2012
    Posts
    10
    Check unit for proper gas pressure, furnace will tell you the minimum gas pressure required for the furnace. But like the other guys said, check air flow, flame sensor & check to see if you have proper draft.

  7. #7
    Join Date
    Apr 2004
    Location
    MN
    Posts
    1,838
    If it's running 10-25 minutes, I highly doubt it is a flame sensor or control board issue. As others have stated, cycling on limit, satisfying call for heat at the stat or plugged/restricted condensate drain.
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