My 1982 Mercedes Benz 300 SD courtesy light over the driver head is not working.
At the first I thought was a bad bulb but it was not. I am not getting 12 Volts there.
When opening any door the lights under the door will go on but the courtesy light will not. Even turning it on manually with the doors closed it will not work. Now I believe that specific light have some device to keep the light on for a while after door is closed. If there is a chance of this device be bad where is it located? If another chance of problem what can it be? All fuses are good.
Thanks.

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Nyck - TX - USA

You must be in the wrong forum. There is not now nor has there ever been anything courteous about a diesel. But, let's wait for those who know about this W126 body style's electrical gremlins

there is a small circuit board inside the lamp body
part of the switch workings there are small capacitors
that fail over time. The simplest solution is to find a similar
lamp in an auto salvage yard as the circuit board under the switch
is hard to get to without stressing/breaking 34 year old plastic.

The circuit can't be removed for service, because of the way the terminals are crimped into the plastic fixture. A replacement is the only way to get it working correctly again. However, if you can live without the timer circuit, it can be bypassed. All you need to do is to bridge the power source around the timing circuit. This will make the lamp turn on and off with opening the door, but without the "afterglow". The photo shows the bridging clip I used on my 190D to accomplish this. A 126 may be a bit different, but I'm pretty sure it uses the same circuit.

http://www.peachparts.com/shopforum/attachments/diesel-discussion/134745d1454802538-how-test-86-300sdl-front-dome-light-img_0306.jpg