The old VW bug uses the same type of fuse M-B uses and the VW always have lots of problems with the fuses blowing. Compared to the VW, M-B fuses are almost reliable - probably because M-B's alternator is a better source of elec. and the generous use of relays to lessen voltage surges (VW did not have relays, or if it did it was only one or two).

On your M-B, when examining the fuses be aware that sometimes the fuse looks OK but when you take it out it falls apart. This can cause an intermittent contact allowing the electrical current to flow, then at other times no electrical flow. If you suspect a fuse take it out of the fuse holder and inspect it, even if you have current as shown by volt/ohm meter and/or the the circuit works. Cleaning the fuse box connections is also a good idea, as recommended by P E H.

Also, the various headlight beams are on different fuses. I am looking at a fuse box info sheet showing what each fuse protects. High beam right is on one fuse, high beam left with the high beam indicator is another fuse, low beam right with fog light (singular not plural) is on another fuse, and low beam left is on another fuse. Your fuse box may be different than the one I am looking at, but the concept is the same - M-B splits up circuits with fuse protection for each headlight and beam intensity.

I would also add that having a water tight fuse box cover would probably help to control possible corrosion on the fuse block connections. Check the cover gasket for cracks, make sure it is in the groove completely, and look for any other problems preventing a good seal.

Good Luck!
Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.