06 Dodge 2500 megacab, diesel. A/C loses charge, I cannot find a leak and have added dye and leak stopper with new charge. Is is possible the high pressure switch is faulty and the compressor is not shutting off ? - is there an over pressure valve on the compressor ?

 

There is a relief in the system to stop over pressure. Do you have access to a manifold gauge set? The leak could also be from the Evaporator core in the heater box