I purchased a used combination switch on ebay, I received it a couple days ago and looked it over, it's looks as if it's almost brand new, which seemed good. Today though I went to install it, but before going through the whole procedure of taking off the steering wheel and lower dash panel I decided to test it by plugging it in to see if it would solve the problem.I removed the panel above the pedals and located the plug, plugged the new switch in, started the car, but to my dissapointment the same problem.

All the lights work, except the low and high beam. This leads me to believe that the switch I purchased it bad or there is some other issue. I emailed the seller to confirm that the switch does indeed work, but am wondering if I can test it myself? Visually the switch looks as if it's brand new, the mechanism also is very tight, not loost at all, which seems like a good sign, though I don't really know what the problem with these switches usually is, if its related to over use, a mechanical problem, or if the electrics just randomly go out.

As far as the problem being something else, could it be a relay, does this car, a 400E, even have a headlight relay? And does the headlight switch ever go out? What kind of electrical testing can I do I determine the cause? I really don't know where to start.

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1992 Mercedes-Benz 400E
2002 Mercedes-Benz ML500