Hi, to all my W210 interior door courtesy lights are not working and neither are my interior lights above the rear view mirror. The vehicle has been layed up since 2018 and no one can remember if the lights were working then. I have checked all of the fuses I hope. Testing the wires at the doors gives me .84 of a volt at one of them and lwer at the other 3. At the overhead lights I get .2 volts. Needless to say that is a problem! HELP ANYONE.

Rod

Do you have any buttons up by the dome light above rear view mirror on some models it operates door lights on front doors . And check out the door switches are operating.

W210 not like older models. The dome lights run off CAN bus.

There are 6 lights in a W210.
The front light above the mirror
The rear light above the back seat
4 door puddle lights

The door switches are hard wired into the PSE pump. The PSE pump not only handles the pneumatics for the door locks but also has a circuit board that has sensors and relays controlled by the CAN bus.

The overhead control panel (where the front dome light is and where the buttons for light control are) is connected to the PSE pump by CAN bus.

The rear dome light is connected to the PSE pump and gets told by the controller in the PSE pump to turn on when either someone opens the door or the rear compartment light switch is pushed on the OCP.

The door puddle lights are controlled by the door controller in each door again via CAN bus.

When you open a door, the switch sends a signal to the PSE pump which puts out a CAN bus message telling all the lights to come on.

So the first thing I would check is that the well under the back seat where the PSE pump sits is dry. Water can get in there and short out the circuit board in the bottom of the PSE pump.

Also check for critter damage since it's been sitting.

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2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

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Jay Bob I have no lights above the back seats but, I have a large moon roof which is probably why I dont. All the other lights are as you say. I will pull the back seat and see. I just put a new battery in a few weeks ago and at that time it appeared dry. I noticed today and every two days the battery is losing charge quickly. I charge the battery every 2 days start the car run it for a while and put it back in the garage. Today it would not even crank voltage check revealed 11.98. By the way the car has always sat in a dry garage.

Rod

I had already checked fuses etc and found no problems. Today i decided to recheck everyting starting with the key. Batteries were low in the key fob and upon replacement all locks now worked as they should. Several fuses were out of place in their respective slots under the rear seat. Upon inserting the # 3 fuse in its correct slot the lights began working. It appears the shop that replaced my ignition switch in 2018 pulled several fuses and then put them in the blank spots more towards the trunk of the vehicle. Hence i was so mad that no one in the family wanted to drive the car once we got it back so it was parked for 2 years. Have been detailing the car now getting it ready for sale.