Correction: In re-reading my last post, my fuse was SUPPOSED to be 16a, but MB recommends replacing with a 25a.

since my 300TDT is a 1981, and YOUR SD is a 1981, I am making a giant leap in assuming that this *could* be your problem as well... In my tiny little mind, replacing a smaller blown fuse with a bigger new one is only masking the problem, but if MB suggests it, I would believe it!

Good luck.

__________________
Current: '91 300TE 4MATIC 317k and climbing...
Former:
'81 300TD Wagon 168K "Tank"
'83 240D 216K 4spd manual "Da Bear" (aka best car ever)

"Never sweat the petty things...
and never pet the sweaty things."