My 86 190E has the exact same problem also. I just got mine out yesterday and put the battery back into it (I dont use it in the winter) but AW, I was going to ask the same question. Where do we need to start looking for the root(s) of the problem?

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1986 190E 186K (For Sale)
(Maroon, Tan leather)
1996 C280 Sport 208K
(Brilliant Silver, Black Leather)
2002 CLK430 Sport 45K
(Brilliant Silver, Gray Leather , Birdseye Maple)