First post here. Thanks in advance!

I have 2000 E320 (w/31K mil). When I shutdown andexit the vehicle (after using the headlamps); the front external courtesy lights do not shut off after 30sec as expected. They simply remain on; thus proceeding the run down my battery.

Took the car into MB and they narrowed the issue down to the vaccum pump (blackbox) located under the rear seat. It appears thatone of the electrical connectors is corroded (actually I think they could take a wire brush to it with some elec. cleaner; maybe even a hair dryer...). Anyway! They we're wondering where and how water could have gotten into that area... the area (pan etc)dosent appear tohavewater residueand the blackbox is actually covered with heavy sound dampening foam... Where could this water have come from? Could water be getting in there via the pump and or hoses?

They won't cover it under my MB warranty as they are claiming "water damage"... The part cost $1000 + installation; unreal! I'm frustrated!

Can anyone help me here before I go nuts?

Thanks much!

Tom

 

This is a common problem. The pump itself can build up condisation.. Also make sure your sunroof is draining properly. I believe there is a drain that runs down that C-Pillar. I remember working on a car that had water leakign in there cause by the sunroof. Cant remember if it was an E-class or a S-class.

 

Hi
I agree with MBZ.
The unit is known as PSE.
However since I don't have specific knowledge on E Class I am also intrigued by how the water got to the module.
This is a VERY common problem on SLK since the water runs down the side of the boot liner when the roof is stowed or left open for a minute or so when raining.

The "damage" occurs when water gets onto the white multipin connector on the PSE and only a minute quantity of water over time causes the problem. This connector carries the CAN (digital highway) and can cause all sorts of apparently unrelated symptoms.
"Cleaning" doesn't usually work since the water seeps inside the unit due to poor gasket design and shorts the internal circuitry which in turn damages some of the components beyond repair.
I believe the water will have reached the PSE down the wiring harness (capillary action) but am unfamiliar with how water could have dripped onto the harness.
As MBZ states condensation may be adequate when "concentrated" by the wires within the harness.
Does you car mist up....i.e. is it damp inside....i.e. blocke plenum (heater air inlet) or similar? or maybe it is the sunroof drain.
Maybe it just rains a lot where you live!

Bottom line. How could water get onto the harness?

 

Thanks for the feedback!

I ordered a new PSE from MB. Being this box is so critical to so many integral functions, I would think this should be a regular inspection item. I know I will be looking at mine regularlyfrom now on. Also, I may put some sealant/goop around the electrical fitments to ward off any future water...what do you think?

Thanks again; I'll be back I'm sure!

BTW, I'm no mechanic, but do you recommend I buy a service manual? What should I get? Where?

Aloha,

Tom

 

Hi,
Afraid that the PSE is not the only "electronics" box that is crtical!! There are about 20+ of them!!

Water and electronics don't mix.
Nothing really to inspect. It works or it doesn't.

Need to be VERY careful with sealant. Might not be a good idea.

Real issue is how did water (moisture really) get onto the harness and then track down the leads to the plug.
Ideally the connectors should be the other way up. i.e. Plug in from the underside.

I do not have any information on manuals.

Stuart.