I am having a major problem with the lighting system on my 01 E320. Several days ago the Defective Lamp indicator light came on and the lights for the Instrument Cluster, Radio, and Climate Control went out. By the way, it was raining very hard at the time. I inspected all external lights and found the trunk light to be out. I replaced the trunk lights with bulbs from Advance Auto, however, trunk light still does not work. I checked the fuses under the rear seat and engine compartment-all fuses appear to be okay. Any ideas as to what could possibly be the problem with the Instrument Cluster lights and Trunk light. Need help.

 

Water (Rain + Leak) and electronics do not go together well.

However something doesn't quite seem to add up.
You say you got Bulb warning light on. OK.
You checked and found blown bulbs. OK.
New bulbs have not corrected the problem.

Therefore there must be more than one problem.
Chances of simultaneous multi defects are unlikely.
Hmmm. Are you sure the old bulbs were blown. How did you check them. Visual or multimeter? If the old bulbs are OK then this makes more sense.

Bulb monitoring is done by the Pneumatic Security Module (PSE) under the rear seat. These do not like water but how could it have got wet?
PSE is connected to other components like the Radio, Instrument pack and Climate thru the CAN (Digital highway). More later.

Next what do you mean by Cluster, Climate control and Radio went out. Illumination went out or function (speedo etc. readings, Radio sound etc)?
If the later these also use the CAN.
If the former than there is a link to the sidelight circuit .

Now that the rain has stopped have things returned to normal....ie dried out?
CAN YOU ADD ANYTHING ELSE?

Is your heater air intake plenum chamber drain clear?
Does the car smell damp/musty.

Sorry can't be of much more help.
Most likely cause is water across the CAN but where is the question.
This problem doesn't always self correct since deposits are left after the water has dried out.
A MB dealer (not a normal garage) can connect diagnostics and SHOULD be able to read codes which should give a further clue as to what has occurred.
Stuart

 

Snanceki, thanks for your response. I removed and visually checked the trunk light bulbs, both appeared burned out (blackened). I replaced both bulbs and reconnected all wires. Illumination had also been lost for the instrument cluster, radio, and climate control. Car does not smell musty and is not damp. I thoroughly checked the car for internal water seepage, non found.

 

I suspect the blown bulb symptom MAY BE a red herring. I believe the bulbs are blackened but still OK. If so then it reduces the field of possible problems.
You have also indicated that the possibility of water + electrics is not the obvious cause.

I therefore suspect a simple fuse on the side light supply side. I don't have a circuit diagram with me at present but suspect that the fuse will be in the engine control box at the back of the engine bay or possibly somewhere near the lighting switch.

Will try to determine which fuse later in the day.
Stuart

 

Stuart were you able to come up with further diagnosis. I rechecked the fuses and still could not detect one that was blown. There continues to be no lights in the seat controls located on both door, the center console with window controls does not have lights, the radio will not light up, the instrument cluster still does not light up, and the license plate lights still do not work. Could the light switch be the problem? Are there fuses located under the dash?

 

Located problem. Blown fuse that was bearly detectable, could see break in fuse, at unique location on fuse. Fuse box was on side of dash, next to light switch.

 

Hi,
I looked it up but you beat me to it!
End Dash Fuse Box.
Fuse 11 (Top Row Right)
Controls Licence Plate, Instrument Pack, Symbol Lighting, Auto Headlamp Range.
Everything now fits. The Licence plate bulbs weren't blown!
Why MB makes life so difficult is beyond me.
If only they had a simple ready recknor as to what fuse does what like on my S Class!
It would also help if they used more "self healing" fuses. (Auto reset).
Question is why did the fuse go?
Glad all now appears OK.
Stuart

 

Thanks Stuart, I appreciate your efforts to help me. MB complicates the design so that consumers are left with no choice, but to have them service the vehicle. Have a great holiday.