Originally Posted by thayer

Here is some information I found while researching the r4 compressor and it's uses on both GM and Mercedes. I found this fascinating.



Re: [MBZ] AC Compressor woes...

Royce Engler
Sun, 11 Feb 2007 21:54:49 +0000

Thanks, Marshall...that's the post I was looking for. I'll show it to myindy and file it in a safe place.Best Regards,RoyceRoyce Engler1985 300TD Turbo 290K-----Original Message-----From: Marshall Booth [EMAIL PROTECTED]Sent: Sunday, February 11, 2007 2:42 PMTo: [EMAIL PROTECTED]; Mercedes Discussion ListSubject: Re: [MBZ] AC Compressor woes...Royce Engler wrote:> Gents,>> I seem to recall a discussion at one time about AC compressors on 123's> being mounted "upside down"...and if not mounted right side up, failingdue> to improper oil distribution in the compressor... Anybody remember orknow> the answer?>> My compressor has once again seized up, and last time I was under there, I> thought I noticed that it seemed like it was upside down from what I> remembered. My indy does all my a/c work, and this will be under> warranty...just had him completely overhaul the a/c system a couple of> months ago, but I'd like to solve the compressor seizeup problem once and> for all. I've probably gone through 4 or 5 compressors in the past 2 or 3> years. After replacing the mono valve and resoldering the ACC board, Iwas> getting real used to the climate control working correctly. ;-(>> Royce Engler> 1985 300TD Turbo 290KThe sure fire solution is to buy the compressor from a parts supplierthat will sell you a compressor that is configured to work on a Mercedes- and if it fails, will provide you with a replacement and the cost ofthe labor!As to the X or lack thereof:> "A word of advice on buying a replacement compressor:> Any one you get that does NOT come from Mercedes will have the frontbearing> cover installed UPSIDE DOWN. Look at the cover on the front behind the> clutch. It will have 4 bolts. Between 2 of the bolts will be an embossedX.> This is the position of the oil hole to lube the front bearing. The R4> compressor was originally designed for GM cars with the compressor mounted> on top of the engine. The X and the inlet/outlet port is UP. Mercedes used> the compressor but rotated it 180 degrees and mounted it under the engine.> This put the ports DOWN. Then they rotated the front cover so the X is UP.> Oil does NOT flow uphill. If you use an aftermarket compressor with the X> down, you will starve the front bearing of oil. It may last a week, amonth,> 6 months.... depends on the quality of the bearing they put in. "I have received feedback on that information confirming that it isbasically correct. That DOES NOT Mean that if you mount an R-4 upsidedown, it will fail prematurely - only that it is much more likely tofail prematurely if you mount it upside down.I have had many people dispute this and tell me that, "I mounted mycompressor without an X on it and it's still working 10-15 years later.No argument, but there really is a reason why Mercedes marked theircompressors and most of the guys I've spoken with that do this for aliving (and don't want comebacks) insure that they use compressorsconfigured to work on a Mercedes.Marshall--Marshall Booth Ph.D.Ass't Prof. (ret.)Univ of Pittsburgh School of Medicine[EMAIL PROTECTED]