I would first remove the lighter/tray assembly and test the power. If you don't have a tester just hook a 12V bulb into it. Testers are very cheap, you can get the little ones at the $1 store. Also keep in mind that the cigar lighters in an MB are not of standard size and therefore the devices you purchase will not stay connected when you plug it in the lighter. I have had to hard wire in all my accessories since the lighter is not a standard size. Other people have inserted non conductive shims in there to make it tigheter, but I would not suggest due to potential heat from power tfr and fire. I think MB recommends installing a separate power socket under the dash for items such as radar detectors and etc.
After you test the power with a bulb or tester (make sure ignition is on) if you don't have power, I think that the fuse also supplies your SRS test system is in the same circuit, does your SRS light come on when you start the car? I have seen people fault the SRS and then just pull this fuse to make sure the light doesn't come on, so check that the fuse is not just missing. There should be a list of item on the back of your fuse panel lid. Good luck.
Brian

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Brian W. Heitman

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