theauxify

Hello guys , can anyone tell me what could be the problem to my w211 number plate lighting ? The situation is as follows:

- fresh bulbs wont work , led or hologen doesn’t matter .
- voltage at the terminals for the bulb when bulb removed is 12v everything checks out
- once i insert the bulb it cuts power to it and it does not work. Could it be the rear sam unit ? Or just a simple fuse problem somehow because all fuses seemed fine to me.
- trunk does open , tail lights work

Heguli

Sounds like there is resistance somewhere. Not so much that multimeter wouldn't show voltage, but when the load is applied, faulty section heats up and no voltage goes through.
Two options; either SAM is faulty, or there is corrosion in some of the connections, or broken wire. I just had similar issue yesterday at work (not MB). I got voltage on the connector, and the solenoid had a correct resistance, but when I plugged the connector, nothing. Took the wiring apart, and found broken insulation where the wire had corroded. Fixed that, and all was good.

Just remembered, I took the tailgate panel off from my S211, and found two connectors that have slight corrosion. Other is closing button connector, and other inside light on the left side.

theauxify

okay i will check this then, going to pull carpeting and check if there are any exposed or cut wires , going to update this if i find something

Heguli

I suspect that there's a grounding issue. If you use DVM to measure the resistance of the wires, positive wires are on the connector number 19 at the rear SAM.

theauxify

That is the same asumption that i had , i just had no clue to how to test this honestly i will check this solution out aswell , going to go thru all the wires in the hinge and near the SAM unit then going to test the grounding . Gonna find a guide on how to do it