DASH A/C Freightliner/Fleetwood/Denso intermittent

Lets narrow the problem down. Stop,the coach when it starts to blow warm. Look at the ac compressor and see if the clutch is engaged and turning the compressor. If it is not then something interrupted the signal to,the clutch. It could be high or low pressure cut off switch. You said pressures were fine. Would you post the readings and the ambient temp when you took them? You could have a faulty clutch. Measuring the voltage on the clutch engage wire would tell you if it were getting a signal to engage.

Eliminate the simple stuff like this first before tearing into the control unit.

Post back and I will help you narrow the problem down.

The mixing valve is allowing the heat to get with the air...check the cold/hot thermostat and its associated systems...it may "default" to hot if there is no electric to it.

I do not recall dash AC's having a thermostat. How did you check the pressure as you say is OK. Maybe icing up and shutting down??