I have a Train XL 1200 and yesterday afternoon it began blowing out warm air. I checked the thermostat and then reset the circuit b breakers on the house box with no repair. Today I checked the fuses on the outside of the unit itself and all was good. I unpluged the thermostat for about 15 minutes to let it reset and it had no effect.
The unit is on the roof and I checked it. The fan on the roof is not working, it will turn freely if pushed. But I hear a short humming sound that lasts about 2 seconds
About every 2 minutes or so.
Any Suggestions?

Could be the condenser fan or capacitor.

It could also be the compressor.

If you have a amprobe take a reading during the time of the buzz to see what the draw is. That will be a determining factor.