Hi I have a 1987 s124 diesel wagon. The previous owner had the AC converted to R134a, and it did not work when I got the vehicle. They'd replace the receiver drier and the compressor. I replaced the AC control unit, the klima relay, the expansion valve, and the black pressure switch. I did not like the pressures, so I replace the receiver drier. There are few specifications specifically for the 1987 so charts have showed me that it either holds 2.18 or 2.875 pounds of R12. Conversion chart show me that for R134 it should hold 1.7 or 2.3 lb. I went with 2.3 lbs. I'm an experienced mechanic and have access to a recharging machine. The car will cool beautifully and then cuts out the compressor. It will not come back on unless I turn off the ignition and turn it back on. Simply using the AC control won't do. I can do this at speed. The pressure will be approximately 20 pounds and 240 when it's running at 2200 RPM at 94 deg, cooling output under 45 deg.
It seems to be electrical but I am stumped.
Any ideas?