I just became a new owner last month. 1985 300sd that I got for a song. Runs great but the hot NC summer makes me want to fix the A/C. The guy I bought it from said the A/C worked but he took off the A/C belt to improve fuel mileage (yeah right). I've turned the A/C pulley and it spins very easily. When I spin the A/c with the clutch it spins but not quite as easily. I've bought a belt to put on and a couple cans of refrigerant. It already has 134a connectors, so I assume it has been converted. Anyone have any advice on putting the new belt on? I haven't even tried yet but I've replaced belts on many cars before. I just want to know if there are any tricks or unseen bolts/etc. By the way, this forum is very informative. Every car I've owned before had a forum and the backyard experts provide way more advice for the DIY mechanic. Looking forward to many more miles on my MB and saving $ on fuel.

Have not done it in a long time but as I remember the alternator is involved and there are about three nuts that need to be undone, one is a pivot. Seems like the tension on this belt is also adjusted with a bolt rather than a big stick. When I replaced my AC in a 1981 300SD it was pretty tedious removing some of these nuts. But you will see everything; it is pretty intuitive.

Although no one would agree that I put the belt on the "correct" way, it is now on. The power steering belt needed to be removed, but that takes about 2 minutes. Now that the a/c belt is on I put some refrigerant in, but I must have a leak. After two cans it only got a few degrees cooler. I drove it for about 20 miles and when I got home the compressor was no longer engaging. I put a little more refrigerant in and the compressor started to engage again. Obviously the pressure cut-out switch stops the compressor once refrigerant is gone. Oh well, so much for an easy cheap fix. Anyone know where to look for a common leak? I think the refrigerant I put in has the UV leak finder, so I guess a black light will help me find the leak but I probably can't fix it. Happy motoring!

If you want your a/c to last for any length of time, you might be money ahead to read up on what it would take to do a recharge. From what I've read, it's certainly more involved than dropping a couple of cans of freon in the system. Most recommend a flush, replacement of o-rings and receiver/drier, then vacuuming the system down for a period of time. Then the freon can be added using pressure guages to get the correct charge.

You now know that the compressor engages and attempts to operate the system. I'm betting it wouldn't take that much to get everything working like a champ. Here are a couple of links that hit on what's needed: http://www.ackits.com/ and http://www.dieselgiant.com/repairyourac.htm

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Sam

84 300SD 350K+ miles ( Blue Belle )

The pic may help.

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83 SD

84 CD

Thanks for the links. When I get time I will try other things since I have a working compressor.