Just had my '89 190E A/C converted and no cooling. The clutch engages for a few seconds, squealing the whole time, and then dis-engages, squealing stops. I'm far from an expert but it sounds like the compressor is developing too much head pressure. Could this be a clogged expansion valve? The mech (non MB) who did the conversion thinks it's electrical - I asked why and he had no real reason.

Any help is welcome!