I am in the process of replacing the belts onour 1979 300SD (we just got from Green Benz-I know-I know) and of course the belts are shot. I have located 3 bolts holding the compressor in place and 1 smaller adjustment bolt, but is there a tension adjustment that will give enough play to remove the belt or do I have to take the compressor off to replace the belt?
I am having the same issue with the generator (or alternator-which is it?) in that I cannot get enough play by backing off the tension adjustment to remove both belts and again, I assume it will mean removing the unit.
Please say it ain't so............................ the oil leaks under there are making this one messy job and all the parts have to be cleaned just to work on them!

 

Might not be a bad idea to remove them, because then you will be able to clean much better, and you will see how it all fits together and then the next time you need to replace the belts, you will know what to loosen. The Alternator has 3 bolts, loosen all 3, and will come loose, remember they sometimes have been in position for a long time, and could just be stuck.

You possibly have a leaking front oil seal on the Crank, will need a Gear Puller to get the pulley off, and be careful not to loose the little key lock, that comes out when the pulley comes off... good luck, I also struggled just a little bit the first time I did it...