Actually, I don't think the pressures look too bad for 1500RPM/stationary/DFW heat & humidity. The old MBs ran pretty hot on the high side.

Might be a bit overcharged - I'd like to see it stabilize at 25 on the low side. But that shouldn't account for the almost complete lack of cooling you are seeing.

Is the low side plumbing sweating? Check the temperature of the high side plumbing, see if it changes from hot to cold before the expansion valve. If it does, you've got a restriction. Has a sealer been used in this system (That one's for Larry...)

This is a 201 chassis, correct? I'm not so familiar with the HVAC system on those. I think they use a more conventional setup with no monovalve to regulate the heater core, but rather use a blend door to direct the airflow across or around the heater core. I'd be looking for problems there. Is it possible to block coolant flow to the heater core, perhaps by pinching off a flexible hose? Might be interesting to try it.


My $.01 (I don't think I have 2 cents worth of advice to offer here...)