Any ideas? (Trane XE90, Model TUC080C942A0, Manu 1994)
Pressure switch works, meaning it is open when the induction fan blows and is closed when it is not. With heat on each terminal reads ~26 volts.
There is a sensor of some type on the inducer fan housing; it runs inline with the inducer motor. I tried bypassing this sensor and it made no difference.
The furnace will produce heat/cycle on and off. The inducer motor however never wants to turn off.