w116 Dome Light conundrum
 

My '79 300SD has an electrical gremlin i cannot identify. The dome light does not work consistently when opening the drivers side door. The passenger side door activates it properly each time. I have replaced the door jamb switch and the entire dome light fixture/bulb and it still only works occasionally. To add to the confusion the glove compartment light also only works occasionally. everything else I can tell works, buzzer, instrument cluster etc and even the dome light if I set it to manually on. anyone else experience this?

Remove the door jamb switch and short the 2 wires. If the light stays on ALL the time then the problem is the switch. If not then it could be the 'brown' wire to chassis is intermittent or something from switch to light. Do the same for the glove box switch. It is just a simple way to do divide and conquer. Good luck.

shorting the wires did not make the light go on, another forum suggested it might be a 'dome light relay' that is faulty & am now attempting to research/replace.
Thank you for the input!!!

shorting the wires did not turn on the light with the Dome or Glove C. another forum mentioned a relay that may need replaced, working on getting that replaced with hope that fixes it. thank you for your help

If the 116 is anything like the 126, the key has to be "on" for the glove box light to work. I bring it up because I thought my car had an intermittent fault until I discovered this "secret". Kind of stupid IMHO since usually you're trying to store something in the glove box after you shut the car off...

yep sure enough, key has to be in the ignition for glove compartment light to work. great tip ty!