The main blower motor was replaced. (It would not move at all) Now it works fine. The burner cycles on and off, but, the inducer fan doesn't want to quit?

 

I have had to replace control board for this problem.
Did the problem start immediately after installing the new motor?
Are you getting any error codes?

I would verify that a wire isn't cut and shorting or that the induced draft motor isn't improperly wired.

 

No error codes. The wiring to the inducer was never touched. It used to work. The entire problem was intermittent. The inducer would run constantly, the furnace would cycle, the main blower would come on(sometimes) sometimes not, and then would trip on the hi limit. So, new blower motor, furnace worked perfectly, for awhile. Now, back to the inducer running full time, except the main blower works well. The temp. In the house is fine. I am thinking that if it were a defective t-stat, the inducer would run, as on a call for heat, the furnace would run but end up tripping on hi limit? The burner cycles as it should and the blower works on and off as it should? A shorted wire to the inducer? K. I thought that would have tripped a breaker but I will need to have a closer look. Thanks.

 

If the control board has an LED and it isn't giving you an error code (like pressure switch error) it points to a faulty board.

 

I'm actually surprised the furnace will even operate with an inducer that is constantly running. Usually the control board needs to see the pressure switch closing after a call for heat. If pressure switch is already activated the board should show trouble code.

Normally a problem/stuck relay on the control board will be the cause of the problem. You can try gently tapping the relays on the control board to see if it returns to normal. This would only be for diagnostics.... if the relay sticks once it will again.

 

I was surprised not to see a "closed pressure switch with no demand present" error code when I ran across this problem.

A new control board resolved the problem for me.