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  • Blower doesn't shut off in Lennox upflow furnace

    I have two Lennox furnaces in my home (one for each zone). As soon as it started to cool down this Fall and we started to use them again, the blower on one of the furnaces stays on well after the heat has reached the target temperature and kicked off. It will run for hours, blowing cool air only until: 1) the temperature drops in the house and the heat kicks on again; 2) eventually turns itself off (after several hours).

    A person I know who sometimes works with heating units suggested that the system is probably very dirty and should be cleaned (as opposed to having a faulty relay because the blower would likely not turn off at all). Anyway, we vacuumed out the system, used some electrical contact cleaner spray and then blew the system out. After running the heater after this, the blower still stayed on for 30-45 minutes after the heat reached the target temperature and kicked off, though this is better than it had been doing.

    We're going to try the cleaning process again, but I also wanted to know if anyone had other ideas about the problem. Thanks.

  • #2
    Re: Blower doesn't shut off in Lennox upflow furnace

    Please list the model number of your Lennox furnace.

    The model will give us an idea of what control system your furnace is using (electronic or solid state) and help us to point you in the right direction...

    Thanks,

    Okie

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    • #3
      Re: Blower doesn't shut off in Lennox upflow furnace

      I only have the information manual that was left by the furnaces when I purchased the house. It lists the manual for units G12, G12E, G12R, G12RE and G12X.

      Thanks!

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      • #4
        Re: Blower doesn't shut off in Lennox upflow furnace

        Im guessing its got a combination fan/limit which is wore out.

        Andy

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        • #5
          Re: Blower doesn't shut off in Lennox upflow furnace

          As an update, we cleaned the unit a second time and retested it. While the blower still ran after the heat kicked off, it only did so for about 15 minutes this time. So, it seems better. I guess my new question is whether this is a reasonable timing or the blower should turn off even sooner.

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          • #6
            Re: Blower doesn't shut off in Lennox upflow furnace

            After the two cleanings and semi-successful tests, we seem to be back to endless cool air blowing between heating cycles. Any advice at this point?

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            • #7
              Re: Blower doesn't shut off in Lennox upflow furnace

              Get a good heating company out to check your furnaces over. Theres a real good chance your heat exchanger is cracked. Lennox G12's are known for that. The problem with your blower is most likely a weak combination fan/limit switch.

              Andy

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              • #8
                Re: Blower doesn't shut off in Lennox upflow furnace

                Maby ductwork is too small for furnace or timer setting on the board is set at the highest setting. Ill go with the limit also

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