Hi Gang,

Once again I am at my wits end here, I need to start with a little background. First I want to make sure its understood this is a 4 door model and the front and rear dome lights work both together and independently according to the demand. When you unlock the car from the remote all the lights come on, when the care is running and you open one of the front doors only the front dome light should come on and when you open one of the rear doors only the rear dome should come on. Also when you turn off the car and remove the key both dome lights should come on.

Ok here we go, a few months ago I started noticing when I'd unlock my car via the remote and then get in and close my driver side door all the courtesy lights would fade out EXCEPT the rear dome light! Sometimes during the day even after driving for various amounts of time I'd happen to look in my rear view mirror and I'd notice the DAMNED LIGHT was on! Interestingly I could do one of 2 things to get the light to go out, I could either reopen my drivers side (front) door and shut it again, or I could hit the overhead rear dome light control button located by the sunroof switch. THIS IS CRAZY!!!

Now another tie in to this, A month ago I moved from beautiful sunny warm Florida to insanely cold Minneapolis. Well one night shortly after the move I happened to awaken to the lovely sound of my car alarm blaring. I ran to the window and I see the car is just fine except for one thing, guess what.. the damned rear dome light was on!!!! I'd let the alarm reset the light would go off and I'd think things were gonna be ok, couple hours or so later it would happen again! After a couple of nites of embarrassment I go out in -20 cold and start fidgeting with the door jam switches thinking ok dammit this has got to be the culprit. Well I went to both rear door switches and pushed them in as far as they would go and the light stayed on. I EVEN REMOVED BOTH SWITCHES and the light stayed on!!! After pulling the last hair off my head I said the hell with this and I removed even the front door switches and finally the light went off.

Well, that seemed to take care of the alarm issue, and I decided fine I will just drive around with no f$%#!^&g door jam switches in my car! Problem with that is you leave yourself vulnerable to break in's and also you can end up locking your keys in the car "due to the auto re-lock feature. SO.. I decided to experiment, I replaced the front drivers door jam switch, ONLY. I left the other three unplugged. Things seemed to be ok for a few days and then guess what... last nite I am driving along and I look in my rear view mirror and the f%^&(#g rear lite is on again! I hit the overhead button and it shut off.

I need help guys, this is insane, is there some damned control module that I can unplug or replace that controls the dome lights? And if so why is only the rear light malfunctioning? CLEARLY it has nothing to do with the door jam switches. My fear is there is a short somewhere that is making things unstable and of course that will never be tracked down "unless" there is indeed a module of some sort and the short is IN the module itself.

At this point all I can say is HELLLLLLLLLLLLLLLLLLLLP

The PSE module is in direct control of the rear light. It also accepts inputs from the rear doors, but the actual rear domelight switch is part of the roof module. That module communicates its desires over the interior CAN ( CAN B) to the PSE. You might try disconnecting the CAN connections at teh roof module to isolate the switch input, but that connector also includes the power to the module so all other functions will stop.

The best way would be to monitor all of this with the diagnostic computer.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Check for moisture in the battery compartment, under the rear seat.

Thanks so much for the info guys, may I ask where the PSE is located? What does PSE stand for and CAN? New to all this unfortunately. Is replacement of the PSE feasible? Expensive? Like I don't know the answer to that one lol.

CAN is "Controller Area Network" and is essentially a serial interface (think ethernet or USB). I have no idea what PSE stands for, but it's under the rear seat, right next to your battery in a foam box.

Water in there is very bad for the PSE and can cause such random behavior. This is (of course) not the only possible cause, but it is common enough.

PSE means pneumatic systems........including central locking & interior lamps

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Thanks so much guys, now if I can just get some descent weather to work in I will start tracking this stuff down!