Originally Posted by Deepsea21

If everything worked before this and fuse #6 isn't blown I'd bet it is a used, defective switch you got. A search on ebay shows new Mercedes switches that these cars use cost about $39. If you have a multimeter you can check for voltage to that connector that connects to the switch at I guess pin slot #6 that would have a pink/red/white wire running into it per Pizza Guy. With the key in the "on" position delivering power to the connector to that switch, stick the red prong into that slot that is gonna be (+) and then touch the black prong to the inside surround of the cigarette lighter that is gonna be (-). You should see 12V+. If you don't have a multimeter great ones can be had on Amazon for less than $10 and there are more YouTube tutorial videos on how to use them than I can count. They look complex but after ya watch a video on how to use one they are very simple. Here's one for less than $10 with the coupon but ya got to watch a video on how to use it. I'd bet 75% of the multimeters sold are blown the first day when someone sticks the prongs into their household outlet without watching a video on how they should be used. They just shove the prongs in without it being set to measure AC voltage (which is the capital V with the wavy line above or beside it). Any other position and shove the prongs into a household outlet and it's gonna be toast on day 1.