A little while back I looked for help with the ac reciever/drier and pipes freezing after about 20 minutes in my 1990 740 (converted to 134). I tried adjusting the low pressure switch, mounted on the rec/drier, but to no avail. I finally broke down and bought a switch at Advance auto parts (about $24.), and compressor is now cycling on and off like it should be, no more freezing (I think). Thanks all.