I would bet the farm, if I owned it, that the amp is bad, seen it many times, actually my 16v is doing it right now. Resloder the connections yourself and it will work again most every time, take your time, use a fine point solder iron and it will be all good. Even after a rebuild shop does the work for the tune of $150 or more, they can go bad again, ask me how I know. i have several in the shop and I solder them up as needed. I have done it 4 or 5 times and it fixed the amp each time. Good luck, dont be afraid of the task, the amp is already bad, it cant really get "more bad". Never heard the bulb issue.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red