RV Repair: A/C unit stuck in heat pump mode, reversing valve, duo therm

Question
When I put the Duo-Therm model #630516.331 in cool mode it blow hot air like it in heat mode.  All other funtions work.  When in heat pump it works correctly.

Answer
Jay, I am guessing that this is a roof mount model. It sounds to me like the reversing valve is either stuck, burned out, or has for some reason come disconnected in some way even if it is just a loose connection. The reversing valve is located under the top cover on the outside part of the unit. If it is good then it would depend on whether it is controlled by a T-Stat or if it has knobs that you turn. If by T-Stat you can test for power inside by removing the lower grill and testing the correct wire for the heat pump side. There are so many changes that Dometic has made with air conditioners that it could be one of many systems they made. But the valve is controlled by 110 ac and if through a T-Stat it gets the signal from the square box that you exposed when you took the inner grill. There should be a wiring diagram on the box and just look for the heat side wiring and you should be able to find it. If this doesn't help you could try and describe the unit better for me, things like how many wires are going to the box inside. There could be 4,5,6, or 7. That would help me better as I would know more then. Also is this a single or multiple unit installation? Thanks, Bill