So maybe it wasn't actually faulty as you suspect.
However WET is a little too generous. Condensation or drop of water might be a better description. The SMALL TRACE of blue (copper salts) on the WHITE multipin connector or on the end of the internal PCB is the give away.

Stuart.

 

I am not sure if this will get picked up on this thread, I realized we are dealing with the old PSE moisture issue.. But, once before I have mentioned using dielectric grease.This is not so muchspecifically dealing with the PSE issue.. It may also be known as dielectric tune up grease, now this is not the old points lube.. Type I use is permatex 67VR generously and religiously on connections. Bazzle, whoI hold in high regard mentioned laquer. I think Snanceki had mentioned something else. What are opinions, input, experiences with this? I have used it for years.
Dumokie....

 

PSE "woes" are due to water ingress / condensation on the wires leading to the PSE unit which approach GEHERALLY from above the unit.

Moisture gets into the boot (trunk) space due to poor seals, damp stowed roof panel or normal ambient cycling in countries (like the UK) with a wet climate.

The problem can be resolved in several ways all of which need to stop the water "running' along the outer insulation of the INDIVIDUAL wires which plug into the PSE. This "water" movement is created by CAPILLARY action due to the close proximity of several wires within the harness.

IMHO the best solution is to keep the boot dry and for addedsecurity to place a small plastic bag over the PSE by cutting a small hole in the base of the bag and securing it to the PSE wiring harnesss with silicon bathroom sealant. (like an inverted funnel)

However I can't comment on whether there could be some strange chemical reaction over a long period of time between the irradiated wiring insulation and the silicon (I'm not a chemist!). I guess ANY grease would work in a similar way and maybe dielectric grease would reduce any risk of a similar chemical reaction between the insulation and what ever water proofing substance is used.
I would not recommend using anything in the plug socket itself since the objective must be to stop the water getting to the plug/socket. In addition many "sealants" MAY cause issues with the CAN signal although dielectric grease should be OK.

Stuart

 

There was no conensation, moisture, spit, **** or any precipitation. Everything was completely dry, all of the drains are clear in the rear. I was told it just "went out". I specifically asked about moisture,they said "no".

 

You may not see the moisture but I bet that is the cause dependent upon the original symptoms which i can't remember.

Usual PSE woes are interior light doesn't work correctly (when auto operation with doors is selected) and the Security system plays up.

However if the pump just fails to produce the required pneumatic pressure this is a mechanical rather than electronics problem.

Since the unit has been changed why not dismantle the old one. I'll bet there are traces of corrosion on the end of the circuit board which adversely impact CAN communication.

However if there is nothing wrong with the unit I dont understand why it was changed in the first place.

Things don't just "go out". There is a reason.

Stuart.

 

My security alarm started sounding when I opened my door to get in or out and the car shut down, trunk wouldn't open. I had to have it towed to MB dealership and they said the PSE pump needs to be replaced and the car needs to be rekeyed for $1200. Everything was working fine until the security alarm went wacky. So I'm not sure what this replacement is going to do besides fix the security alarm? I have a SLK 230 2001. Also, when driving every often I'll be cruising along and the car will suddenly brake and the wheel turns then the BAS/esp lights up. It's very nerve wracking. Is this problem related and will it also be corrected. It happens everytime I drive the car. I just bought this car 6 months ago and have several problems, including the convertible roof won't work I expected more from MB.

 

I had the same problem with the sudden braking and BAS/ESP light. it happened a few times. The last time it happened I was driving downa one lane hill/cliffside and it locked up and pulled me almost into the guard rail and over a cliff. Found out the problem was the Yaw rate sensor. It determines the pitch and yaw of the vehicle and will automatically brake if it thinks your car is rolling or something? not sure totally but it was malfunctioning. Hopefully that helps.