a variable speed dial control was installed on one of the speed taps and wire to CF on the control board. Constant 120v is supplied to this for year round air circulation. The red speed tap is on H but now has no voltage after the furnace has come up to temperature. Running power off CF and H at the same time. Is this the reason why 2 control boards have quit already on me?We have heat so long as we keep the blower running all the time. 2 different heating contractors have worked on this furnace. I am told that i need a 3rd 48k98 board. Should i remove the CF tap off the board so i dont hurt another board? Thank you in advance.

Asked by roberto on 11/27/2008 1  Answer

ManualsOnline posted an answer 16 years ago

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0 Take off the speed controller, you dont need it. The motor has 3 wires, usually blue, red, and black. black is usually high speed whereas red is medium. The speed controller is destroying your motor windings and shorting out the board. The unit was not meant for speed controllers as to the reason for the different speed wires coming off the motor. This should solve your problem if it hasnt been fixed already
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