Mine lights up just like all the other switches. There either has to be a fiber optic for it or a bulb in there. I'll pull mine when I gett he car back from the windshield replacement and check, since I have a 1992 300ce it should be the same.

alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon - Sold
2006 E350 Wagon - 368 - Dead
2015 GL350 Bluetec - 197U