I dealt with a string of problems with these units, which had a 100 percent failure rate. As far as i know i am the only person on earth who has a permanent solution without replacing the unit.
I am speaking of the 1st gen revolution combo units which were FA heat/cool with the W2W heat option field changable to upflow/downflow and left/right return.

If you have one of these problem units or know someone who does, please contact me.