I have always wondered what that red "bulb" socket was for also. It is only on the newer W201 and W124 car instrument clusters, something like 1991 and newer I think. I have never been sure what it does or what it is for either, I'm interested....

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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