Many of these vehicles suffer from too much current on the fuse for the a/c compressor and blower. M/B came out with a fix for the problem that included a separate cable and 30A fuse in a holder outside the fuse box. It's a proper modification and it's not cobbled up by the PO.

Finding it it a bit tricky. It will live behind the dash and below the fuse box. The leads for the cable will properly attach to the screws in the fuse box that are used for the old fuse.

Try to get under the dash and have a look around. You're looking for a cable that's screwed into the bottom of the box with a fuse holder in the middle of the cable. The fuse holder is a square plastic box.