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  1. #14
    Join Date
    Feb 2010
    Calgary, Alberta
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    Quote Originally Posted by Itstartedasacc View Post
    Lennox started using a universal board a short time ago and sending four different wiring harnesses to replace on the different furnaces. I had to replace a board on a g61 and the original board used 11 of the 12 pins on the mullinex. New board used all 12. Blower always ran till I figured out the old harness wouldn't complete the limit circuit. Changed harness and shagged a$$ outta there
    That's not a universal board, it's an update to bring the dash 6 and below G61 up to the dash 7 and later style board/igniter.
    Same with the G32.

    Think that's bad? Just wait til you have to start carrying parts for their new furnaces.
    The ML193 is up to -4 and has 3 boards, none are cross compatible.
    Then there's the pressure switches

  2. #15
    Join Date
    Mar 2015
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    I had this exact problem when changing out the Ignition control on a Lennox G20 Whisperheat. The original module was a Robertshaw 735L. I replaced it with a Robertshaw SP845 780-845. The 735L was starting to buzz pretty bad so I sought out to replace it. After replacing it with the SP845, the ignition was perfect and the buzzing went away. I was high fiving myself. After the furnace shutdown, the fan would not stop running. Checked all connections which were fine. Tried swapping the limit and W leads as mentioned earlier on the BCC, no fix. The BCC board was the original LB-63622A. Fortunately I had the updated BCC ( 48K98) as a spare. I figured the SP845 is not completely compatible with older BCC boards so I installed the 48K98. Bingo Bango, using the SP845 with the 48K98 shutoff the fan properly after the heat cycle ended. I'm sure your buddy fixed his furnace one way or another since its and old post but this is good info for others seeking help on the internet.

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