It's a 2004 E320 sedan.
I have been all over the trunk, under the rear seat, and cannot find the PSE unit. I've read where if water gets into it or it's damaged the car will do odd things.
The dome light comes on all by itself, the alarm sounds (and is difficult to turn off) when unlocking the car, and I've had the sunroof open by itself.
Sometimes I think this car is possessed. I live in Washington state and it's the rainy season - the car was fine all summer, I've only had it since June.
I did find water under the spare tire, so I know I've got some issues there, and I'm thinking water might have gotten to the PSE but..... I just can't find it.
Does anyone know where it is? Thanks!

 

the pse controls pneumatic operations, it kinda sounds like your rear Sam has taken water damage. id get codes read at your nearest mb dealer

 

I'd like to be able to remove the unit myself, be able to test it and maybe resurrect it. Or at least buy the part and replace it myself.
So I'd rather just find it and go from there.

 

Ummm...The W210 models have the PSE pump; the W211 uses electrics, not pneumatics. With both a W210 and a W211 I've gotten far too familiar with both systems when working on the locking system. You have water infiltration into one of your electronic modules. STAR would be recommended to see if it will identify the faulty module (look for stored and current codes) and by unplugging modules one at a time until the problem quits and the CAN bus shows "stable". You then replace that module. Be aware there are approximately 32 digital modules in a W211 (depends upon options).

The overhead control panel (OCP) N70 (assuming it is the front dome light illuminating plus your description of the sunroof opening) is controlled by the rear SAM N10/2. If you have water infiltration into the trunk, you need to check the rear SAM's connectors for moisture. You will most likely find the source of the leak under the gasket at one or both of the lower corners of the trunk opening. There is a plastic piece that guides water under the trunk lid and dumps it onto the rear bumper; if the opening gets clogged with dirt or leaves water will seep under the gasket. Bubbled paint and/or rust is the tell-tale sign when you lift the gasket off. Wouldn't hurt to see if water is infiltrating the overhead control panel due to clogged sunroof drains; if so, water in the OCP would make the rear SAM receive signals indicating you were manipulating the OCP switches.

The alarm could be due to a failing internal alarm battery; in that case all you can do is R&R the alarm under the fender liner on the passenger side.

The only pneumatic pump (I'm not counting Airmatic) in the W211 is the one located in the trunk and used for the rubber bladders in the seats; it does not connect to anything else.

 

Thank you! It was driving me crazy wondering why I couldn't find it.
I'll check the trunk drains, since I found water in the well earlier.
I'll have to search for a map of the modules, I guess also.

Thanks again for the help!

 

PM me with your email address and I'll send you a map.