David, I was mistaken, it is a 14mm (apparently 17mm was used on earlier SLs). Yet, I still can't reach the nut with a 14mm long socket, it can't slide all the way to the nut because it can't slip under the compressor.
Gus, thanks. Sounds like a cannulated socket/wrench you're talking about, but wouldn't help me.
David, I wish that I could see your set up, sounds like you have more room than I do under your compressor. I am using a 55amp alternator, but I'm pretty sure it's the same size as the 35amp.
Could be my belt length, which will determine the angle of the tensioning strut; but I am using an MB dealer supplied belt designed for the alternator in its factory position.
I spoke to Gernold who says he sees this all the time and he has to remove the compressor to get to the nut. Actually, he has an even harder time than I do because he mounts these compressors so that the hoses point down so that he can route them under the manifold and hide them. When he sets up a new belt, he won't even charge the A/C until the belt is tightened up after the break in period.
He says that he's working on an improved adjustment setup for the alternator that's more easily accessible.