If i remember correctly, the stock fuse couldnt handle the load of the acc system so mercedes fix was to add an exterior fuse strip that is rated at 30amp instead of using the fuse box fuse that was rated at 20 or 25amp. The fuse box is totally bypassed. They didnt need to "split" the current. They needed to use a more robust fuse.

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VegStew
1983 300SD 70,000 WVO Powered miles
1990 300D In driveway with Head Off - Cracked