That's the dimmer for the lights. Remove the screw holding it on, and pluck it out. Try spraying it with contact cleaner. The EPC stuff is okay, I personally prefer DeOxit by Caig.

If that doesn't fix the issue, you need a new dimmer. I have one I pulled from a junkyard if you need......

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-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition