Robert T....My Dometic Heat pump (rear air) in my 05 Diplomat was doing something similar. It would more often than not come on hot, like the heat pump was on. After posting here, I was told that the system defaults to the heat pump. There is a reversing valve with a solenoid that sits atop the valve that reverses the flow when you turn on the A/C. When it's malfunctioning, it will want to go to heat pump mode.
I went to the PPL website and located the parts for my A/C unit by serial number. The reversing valve was still available. It's simple to install. Unscrew the old one (single screw) and screw on the new one. It's located right on top of the unit when you remove the cover.
I now cycle that rear unit on more often to keep that valve from going bad.
Don & Mary
2019 Newmar Dutch Star 4018 (Freightliner)
2019 Ford Raptor