Thank you Jerry. That leads me to my next question.

We have OTR A/C and the switch for the control is a 3 position rocker switch. Off is in the middle, up is A/C, down is heat.

When we purchased our bus the fellow that ran through things with me suggested that in the winter when needing heat not to put the switch in heat but always in the A/C position and with the thermostat set warm it will in fact give heat and the windows will stay defrosted better in this position.

I never practiced this because I was concerned of doing harm to the A/C compressor but I guess from what I now know this is probably a better way to go.?????