Water in the PSE unit

[Mohnish]

Greetings,

The rear dome light would not turn off on closing the doors. Zeroed it to be related to the rear right door. Figured it was probabaly the door switch but it wasn't. Proceeded to check the connectors at the PSE and in the process when I removed the PSE I found the PSE plastic casing was wet and further the lower half of the sponge casing (box) that the PSE sits in was seriously damp, however the floor area was dry. I figure the sponge was soaking up water. My indy thought it prudent (though, more expensive) to install a new PSE. Everything works fine...for now!!!

In the process of opening the PSE I found the following:
(1) The unit had been opened before (telltale screwdriver marks on the plastic housing and some non OEM soldering on the circuit board).
(2) The whole thing had been wrapped in a bubble wrapped plastic bag (definately not OEM!!!)

This leads me to believe that water had found its way into the area and the previous owner/mechanic had repaired the PSE and then wrapped the thing in plastic to protect it from water damage in future. Over time the plastic tore and water got in again. Unfortunately, the source of water into the area was never plugeed, else I would not be posting!

So this is where you'll could help me out...Where possibly could the origin of the leak be? There are no telltale water marks any where in the area.

I really need to plug this, else sooner or later, I will end up with another failed PSE...Very expensive.

Thanks in advance.

 

[grober]

there's this post which refers to an SLK but may give some ideas? PSE - Removal, Refit and Check - Benzworld.org - Mercedes-Benz Discussion Forum
you will have to register to see the pictures. The poster there blames either blocked drains or failed/worn boot seals. When damp does get to components there are several approaches. one is to attempt to seal the unit, but as you have seen poor sealing can end up being the source of the problem since once water gets in it makes it doubly difficult for the component to dry out again. The poster tries 2 alternative approaches
1. strips the unit and dries it out
2. drills extra holes in the base to allow drainage[and possibly the foam which is there primarily as a sound deadener?]
3. coats the PCB+components
with a water proof lacquer.
4.reassembles the unit

5.checks all local seals and drains for blockage leakage ( you can do this with a torch inside the boot while an assistant plays a hose on any suspect areas) the other possible source of a leak would be the rear windscreen surround or rear light clusters

 

[Mohnish]

there's this post which refers to an SLK but may give some ideas? PSE - Removal, Refit and Check - Benzworld.org - Mercedes-Benz Discussion Forum...

Thanks Grober, though the unit in my W210 is situated under the rear seat on the right side (near the battery) whereas the SLK it seems to be situated in the boot area, as you said it does give a few ideas regards prevention. Thanks again.