baldsparky

I appreciate from researching the forum that the PSE pump is the power house behind a multitude of gadgets on our S classes. Central locking, soft close, rear head rest lowering and the seats lumbar supports all seem to be provided from this source via vacuum style suction.
My problem started when I was demonstrating how cool the soft close system was opening and closing the doors, also folded the rear head restraints down which all worked fine.
Leaving friends for the drive home I noted the remote central locking had stopped working. Same symptoms I have read on various threads on the forum.
ie The alarm arm disarm works fine but no soft close and no central locking.
To cut to the chase the 20A fuse yellow job under the rear seat had blown.
I replaced it and all seemed fine for a short time but now its blown again.
I replaced it, and this time it hasn't blown, but I noticed the drivers door when soft closing seemed to pull in really tight. Then it released.
The central locking and soft close then stopped working again.
I think what is happening is the pumps over running and then either timing out or the fuse blows.
My question is, is there some device like a pressure switch that is suppose to cut the pumps supply when the vacuum has built up.
Also is there any write up that goes through a step by step diagnostic procedure to try and isolate the problem.
I love my S class but some of its gadgets just appear complicated for the sake of complication. I know that can lead to big bucks unless your prepared to have a go yourself.
This Forum is a life saver when it comes to these kind of issues and for that you have my eternal gratitude.
Thanks in advance for any pointers guys.

baldsparky

Ok some more info (been trying to sort this)
After leaving the 20A fuse out the system seems to have re set.
I am deliberately avoiding the soft close feature by closing the doors firmly, so not leaving them on the latch to pull in (soft close)
I have also gently bent back the tab with the hole in the centre on the fuel filler flap, and replaced the original fuel cap with a lockable one. That way I can always open the flap regardless of central locking status. And I have the added peace of mind knowing my filler cap is still secure. (Now lockable)
The central locking is working fine like this, so it appears it may be the soft close feature that is over burdening or causing the PSE pump to over work for some reason.
I cant hear the pump running with the above methods, but then i would think the central locking doesn't require much vacuum from the pump anyway.
Mention all this in case it helps someone help me, or even others one day.

baldsparky

Tried the central locking this morning and all four doors working ok. Have still not used the soft close. Just trying to eliminate the problem.
Also does the PSE pump store compressed air in some way similar to the airmatic system ?
I only ask because surely without some form of air pressure the central locking wont operate.
If air pressure is needed then the PSE pump must be operating without overloading itself or timing out which is a good sign I think ??
So assuming the system is fine just using central locking and problems only occur when I start opening and closing doors.
Does this help to narrow the problem down ???

gmphertford

The PSE pump sounds like it is faulty and requires replacement, drawing to much current when operating, have changed many before because of blowing fuses.

baldsparky

Many Thanks for your reply gmphertford.
As you would know these pumps are not cheap, and to be fair, I don't think its an electrical problem with the pump motors armature or windings.
The way the fuse blows seems to point to the motor being under mechanical overload, and drawing to much current because of that loading.
To add more information what appears to be happening, (I noticed this yesterday) Is that when I closed the drivers door it seemed to suck in very hard and hold there for quite a long while "about a minute" and then the door slacks off.
During this time you can hear the pump working hard in the boot and then it seems one of two things can happen.
A) The system times out leaving the fuse intact.
B) The fuse blows.
Either way the result is the same, central locking and soft close stop working.
I re set the system yesterday by leaving the fuse out for about an hour.
Since then all seems good and the soft close on all doors is working as I believe it should, ie the doors suck in and after about a second or two release very slightly but leaving the door fully closed and sealed.
So it looks as if whatever is responsible for regulating how much pressure build up, and how long the pump should run before switching the PSE pump off, has sometimes failed to do its job.
So it leaves the pump working hard until the safety time out feature operates or the fuse blows.
With all this in mind, my question is what governs or controls the pump from over working ?
I'm hoping that its because I haven't been using the car very much, something mechanical has got a bit sticky and with use it will free up,and sort itself out now I have re set the system ??
Many Thanks, I really appreciate all advice on this.

Welwynnick

Happens all the time.
You can recondition these pumps quite easily.
Just dismantle, clean and re-assemble (though it takes a long time)
They get clogged up with their own internal wear debris/dust.
Anyone can do it, but you have to be careful.

Nick

trombone

Before you mess with the pump, turn the lumbar support switch to zero (both sides) and see if the soft close comes back after 20 -30 minutes.

The lumbar pouch often fails (deteriorating plastic), if so the pump works overtime and blows the fuse or may burn out.

It is worth testing.

baldsparky

Once again, Thanks for the replies guys.
I have re set lumbar supports to 0 all sides front and back !! (showing off now) lol.
Each time the lumbar's deflated with a Pssssss sound, so my guess is they were all holding pressure.
Since the re set (fingers crossed) there have been no further problems to date.
Post 1 explains how this all started, but I forgot to mention that when I drove of the passenger door was ajar with usual dash warning sign and dong. I may have got to a speed that would have brought in the auto central locking before stopping and closing the door properly.
possibly, some how, the systems computer became confused and messed things up. So its possible the re set was all that was needed.
I still reckon that the pressure regulating switch with further research appears to be inside the pump unit with some kind of knurled nylon adjuster may also have failed to operate in time, causing pressure to build up and creating mechanical resistance, which would then overload the motor.
If I need to strip the motor out I will, but for now !!!!! its a waiting game.
Thanks once again for all your help.

Welwynnick

Rather than crossing your fingers, you can tell whether the pump is working properly or not by watching the soft doors closing.

When the door is pulled in, the pump runs until one of two things happens:

1) The pump output reaches a pre-set vacuum level, then it switches off.
2) The pump runs for a maximum time, then it switches itself off.

You can see this behaviour in how long the door is pulled inwards against the door seals, before it relaxes slightly against the latch.

If the pump is good, it reaches vacuum quickly - in a few seconds - then switches off.
If the pump is weak, it never reaches proper vacuum, and holds the door in for about ten seconds, before switching off.

Nick

baldsparky

Thanks Nick,
Looks like the pump is good. It pulls the doors in within seconds and then relaxes.
In fact when the system timed out (before I did the re set) The pump ran for ages and I honestly thought the drivers door when closed was going to implode.
You would have thought I was in a submarine that had dived down well beyond its depth limits.
A bit like the old world war 2 films, when they tried to escape from depth charges, all that creaking and groaning.
Anyway I digress, the point is since re setting everything seems to be working fine.
As said messing about with the soft close doors operating the rear head restraints and finally driving off with a passenger door left ajar by mistake, seemed to start the problem of blowing a fuse, and then causing the pump to over run and time out.
Hopefully the system is no longer confused, and the re set has done the trick.
So far so good, went for a meal with the wife and mother in law earlier, and once again everything seems fine.
One other point, I have decided to leave the fuel flap so that the steel lug doesn't engage with the locking pin and lock the flap closed if the central locking should decide to fail.
I have now fitted a good quality locking fuel cap in place of the OEM unit.
So the filler flap can now be opened any time,and the filler is still secure because a locking cap is fitted beneath it.
Saves all that nonsense of having to remove the boot lining to get to the emergency filler flap release, if caught out.
I think Mercedes could have designed a more accessible way of getting to it considering its secured within the boot anyway.