My ac compressor seems to be leaking from the rear out of a 1/2' - 3/4 inch indentation with a snap ring holding something in. Is there an o ring or something under that I can change to stop the leaking? Thanks!!

Yes there's an o-ring in there. In some GM applications there's a switch installed there, but for MB's it's just plugged off. You'll have to remove the freon first it's under pressure.

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82 300SD 202K
82 300SD 233K
83 300TD 340K
82 300TD 98k euro (parts on the hoof)
85 300TD 282K
83 300TD 197K

Thanks! I was hoping that would be the case.