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.
