• Won't run in auto position

    Mar.3.2010

    My furnace is working properly, but the blower will only run in the on position. When I put it on auto the unit will light up and heat. The fan limit switch rotates and makes the first click which should start the fan, but after the click the fan will not come on. I can reach over and switch it to the on position and it will heat properly. Can you please help me figure out why it will not run in the auto position?

    James, Luxora, AR

    It sounds like you have the older fan/limit switch on your furnace that has three pointers on a round dial. The first pointer is the fan shut off. The second pointer is the fan on. The third pointer is the high limit. I would try lowering the second pointer to a lower setting. If this does not work, most likely the limit control, which tells the fan to turn on when the heat exchanger reaches a certain temperature, will have to be replaced. I suggest you contact a professional HVAC contractor to troubleshoot this issue.

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