I inherited evidence of an overheated fuse 8 from the PO(s) in my '83 300CD - no fuse, just scorch marks. At first I was pissed because I thought I had been scammed during the test drive because the A/C "worked" then. Then I was confused because the blower still worked even though fuse 8 was removed.

A little investigation through the service records showed that fuse 8 was replaced with a fuse saver (from the original owner's notes). The original owner (I'm #3) actually wrote down dates and mileage of each time fuse 8 blew.

The p/n for the "fuse saver" installed in my car is an MB harness A 126 540 3013. It shows up in EPC net in 124's and 126's but not in 123's. I think I read there was a TSB about it. It installs the strip fuse holder 123 540 0450.

My understanding of the correct routing is that it completely replaces fuse 8, so if you've got the mini-strip fuse box installed on the left front fender near the relay box you should not have a fuse in position 8.

From previous experience with a stuck wiper motor, it's not "excessive current" that overheats the fuse, since that would cause the fuse to blow unless it's faulty. It's a more complicated "excessive time near, but not over, the design limit of the fuse." By design, the fuse is supposed to be the weakest link and blow, but through corrosion or dirt it becomes a little high resistance heating element instead.