Trunk central locking misbehaving
 

Hi. Long time lurker here looking for some help.

I have a 2001 clk55 amg coupe with circa 40k miles. It's great - I love it. One of its problems - as winter comes in and the temps drop here in the North East - the central locking gets temperamental. I know this is a common problem and I've read all about the issues people have - I can't figure if none is the same or slightly different - that's what I'm looking for help with.


Ok - so as the temps drop, I hear the pumps or the locking cycle periodically when driving along. And it takes a few presses on the remote to lock the doors. Sometimes I won't lock at all with the buttons. - it needs a key in the lock. . So far - this is standard stuff. As it gets really cold, my trunk refuses to close if it's been opened. That's what I've not read before. I know the trunk locking and latch is off of the same unit (two different microbore hoses from what I can tell) and when I manually apply a pressure of >8psi or so to that microbore pipe, the trunk opens. And it stays unable to latch closed until I release that pressure. I can see that when I apply vacuum to the relevant hoses, my car locks and (positive) pressure unlocks.

So. I've been thinking all along that the trunk lock or rear headrests (appear to be fed from the same supply on the pump unit) are the issue and once I fixed an air leak in those, my problem would be solved. But when I apply a pressure or vacuum manually here, that pressure is holding until I release it. Which I guess points me back at the pump unit itself malfunctioning. Does that make sense or does anyone have any suggestions to guide me here. Thanks in advance.

Craig

I suppose part 2/ 3 etc of my question would be

Should it cycle and should I hear it pumping periodically as I drive the car (assuming I'm not doing anything to the locks/ lumbar control etc or is that symptomatic of a leak somewhere?

Does anyone have a schematic of the pse pump, both what microbore connectors do what- I think I've figured it via trial and error but would love confirmation and also internally

recommendations for places that can overhaul/ repair it. - I've read that it costs $$$$ to replace at MB and would prefer not to spend a fortune on this.


Thanks again in advance for any help. This had been a bit of an issue ever since I bought the car so it's time to get it fixed!!

So as an update - disconnecting the microbore hose that control the trunk and 2 rear headrests and plugging that exit from the pse unit appears to solve the issue of the central locking being hesitant. Of course, now the trunk won't open and the rear headrests won't collapse, so I haven't solved my problem but I may have hopefully isolated the cause of it. Going to drive it for a week or two like this and see if the central locking works more reliably. I'm now back to thinking my issue is the trunk latch. But I suppose it could still be the innards of the pse unit. Once I've isolated it to this specific set of 3 things - i'll add them back one at a time and keep verifying whether there is a problem.

unfortunately, my woes weren't solved by the above. it was looking so hopeful, but Sunday showed me that the unit is just as temperamental with the trunk and rear headrests isolated from it and the hole from the PSE unit plugged. I now suspect the unit itself as all the microbores seem to hold a manually applied vacuum fine.

Still no luck. I pulled the vacuum unit and sent it off to be tested: fixed by a company called programma inc in boca, FL. They tested it and reported that it's fine except some solder that they retouched to ensure proper conductivity.

I refitted and it initially seemed all was well. Then used it to commute this am - same exact thing. Well, trunk didn't fly open/ refuse to close but the central locking isn't working right. - it takes 20 pushes on the lock button before it locks.
So im back to the hose or the actuators leaking air/ not working correctly . I guess my next step is to terminate all the exits in the PSE unit except one and go through them one by one until I see which one is causing me issues. Does anyone happen to know the hose internal diameter?

And should I hear it pressurizing itself randomly whilst I drive? I'm assuming not. If I'm not using the air for anything, one would assume it shouldn't go anywhere and once it's pressurized, it should stay that way until I do something (doors, seats, rear seat headrests ) that uses air? Does that sound accurate?

Final thing. Don't suppose it makes any difference. But my 01 clk55 is actually from 02.

https://cimg7.ibsrv.net/gimg/www.mbw...77aefff7d.jpeg
https://cimg8.ibsrv.net/gimg/www.mbw...768bd7a5d.jpeg
I know this is an old thread but I'm having the exact same issues. My pump cycles every couple of minutes while driving. All of my locks work fine and my bolsters all hold pressure as well. I did a quick visual check at the pump and nothing stood out except for the port labeled "SRU" did not have a hose going to it, nor were there any hoses disconnected....vent port maybe?

If someone could point me in the right direction to troubleshoot this, where to find a drawing of the vacuum sys, etc, it would be much appreciated! Thanks!