Yesterday I turned on my heat(coil in air handler) and everything worked fine. Last night I turned it on again and the fan wouldn't come on no matter where the switch was: fan only, heat or air. I made the appropriate temp changes for heat/air. There is a humming noise coming from the heating coil area. The coil area was getting warm. I can spin the blower wheel easily. There is a Honeywell humidity control next the t-stat and it was in the "ON" position. The wiring diagram shows a fuse near what I think is the printed circuit board box and I found a red cover labelled "buss" I couldn't get the cover off to see if there is a fuse under it. The unit is a TRANE TWE030C140
Any thoughts
Thanks
Roger

Bad PC board or fan relay is my guess.

When I switch the breaker on I hear a "click" which I think is coming from the "contractor"and the hum from the heating coil area. This is after I turn the Humidity switch to "ON".
Is there a way to jump the fan relay? BTW what does the fan relay look like?
Thanks
Roger