ac compressor clutch, '98 E320
 

First, the simple questions: Is it prudent to replace just the compressor clutch on a '98 E320? All of the parts sources I can find are clutch/compressor units. If I can replace just the clutch, does anyone know a source for the part?

Second, there is a good part of the story, it's one reason I keep buying and driving Mercedes:

Just did a long drive (1,000 miles) in very hot conditions, got to destination and noticed a bad "bolt in a tin can" rattle from front of engine. Turns out it was the chain tensioner, which was visibly dancing on the reverse-threaded spindle. In Hilton Head, without tools, pulled into the dealer there (Modern Classic Motors) at 4:30 on Friday. The service manager and tech, even though both were as busy as you can imagine on Friday near closing time (even busier than you can imagine: there had just been an armed robbery of a nearby bank and the getaway car was an ML!, detectives were swarming the place), took the car in straightaway. A quick search turned up a new tensioner, I'm looking at maybe $300 plus $200 labor, so I sit down to moan about not being able to fix this myself. 30 minutes later the tech drives my car back around, hands me the keys and says all is good. I go for my wallet, and he says no, thanks, welcome to Low Country and Hilton Head: no charge! Apparently the retaining nut on the spindle had come loose and set itself free somewhere on I-75 in Georgia. The tech pirated a nut from the new tensioner (it is a special reverse-thread 9.5 pitch one-off), installed it and said he was just glad to save me some money. True story.

Now the bad part: the tech said that I would soon need a compressor clutch, it was making a faint rattle that was masked by the tensioner. His opinion: no problem to make it the next 1000 miles, but it would need to be replaced soon. Got back to Atlanta and the thing is now making a very loud chatter. AC works fine, but is better at low speeds, consistent with clutch slipping. Which leads me to the questions I asked at the beginning of this diatribe.

Thanks for your advice,

Greg

The clutch air gap may need to be adjusted. If the clutch is truely shot, replacing just the clutch is a valid repair.

Moneypit, thank you. Do you have quick procedure for adjusting air gap? Or is it intuitive?

Thanks,

Greg

I don't have the specification for your compressor handy, but on my car it's 0.5–1.5mm. I'd suppose yours would be similar. If you need to, adjustment is by adding or removing shims to move the spring plate in relation to the pulley.

ON the 1996 & later cars the clutch stays engaged ALMOST all the time the engine is running!

rarely DOES THE CLUTCH WEAR OUT!!! But the compressor will.

MB Doc, I hope you are wrong...
 

Thanks for the warning, I am also very skeptical that I can get away with just repalcing the clutch. The car has 125k miles, original compressor, AC works fine, and the noise (clatter) is clearly coming from the clutch. But I understand that the compressor is almost always engaged, heck, here in Atlanta I think it is running 99% of the time, so if I am buying time I am not really counting on getting that much. Your advice is appreciated,

Thanks,
g