My 1994 E320 A/C was working intermittently, cold one day, warm the next.

Took it to a Shop: Tech replaced A/C Relay and stated that it still did not work. It has not worked (even intermittently) since I got it back from the shop. The A/C Clutch comes on for 2 seconds, then cuts off each time I turn on A/C.

I bought a A/C Low Pressure gage to do a little investigating myself. The low side pressure is 80 PSI! I measured the pressure with engine off, since the clutch does not turn but for a moment.

My guess is that the Tech tried adding 134A to the system, but added too much?

Questions:
1. Is 80 PSI way too much (with engine off - low side)
2. What is proper pressure?
3. Can I remove some 134a myself? How? I hate to take it back to those "Techs".

Thanks, John