Hello all,
After reading all of the comments in this thread, I thought I'd post a problem I recently ran across... A friend of mine has a 240D and AC that didn't blow very cold. Also, he complained that his aux fan wouldn't turn on. He brought it over, and we checked it out, with the thought of adding some R12, but when I put it on the Napa ATC 5000 machine, it only showed 57 psi on the high side, 30 on the low side. Output air was around 55 degrees, ambient around 75. Thinking that it might be low on R12, I added a few oz, but this only caused the belt to slip. Further diagnosis showed that the compressor outlet pipe was very hot, but the high side port on the 240D is on the other side of the engine, after the hose that goes under the engine. The condenser was hot for the first 2 inches down from the inlet, but by then cooled very rapidly, and the receiver/drier was cool. All this indicated that the real problem was a defective hose from the outlet of the compressor to the other side of the engine. I have seen this hose fail before on other vehicles, the oil apparently causes it to expand and close itself off. So, keep in mind that there are many ways for systems to fail. Keep an open mind, and remember the temperature/pressure charts will tell you the facts when working on AC systems!
Richard Wooldridge
'82 300D/4.3V6 (converted to R134 with engine conversion, works fine in the NW)
'77 Jag XJ6 (Alternate refrigerant for 5 years, no problems, great AC)
'89 Astrovan (Dual air with R12, works extremely well)
'85 GMC S15 (converted to R134, works fine, fingers crossed w/R4 compressor - I don't think R4 compressors and R134 like each other, though)
Etc...