Central Locking Pump Woes W210

[ronwyer]

Well, I'm now about onto my 4th used pump in as many months to solve an inoperative trunk lock. Today I opened it to go to the store, and upon returning in 30 minutes it no longer works. Same MO yet again. Everything else on the car works fine that uses vacuum, the trunk opening feature just craps out on me.

I have 6 of these, varying model numbers all look the same. They all work at first, then the trunk lock issue comes up. I am assuming the pump runs in reverse to generate pressure instead of vacuum? Sine I am in California there is no water issue. I will open up the pump on one to see what it looks like. Is it possible the pump needs much higher pressure to work the trunk release than to lock the doors? Or is it possible that the doors operate on simply reversing the vacuum circuit to suck them open or suck the other way to lock?

This would not be quite so annoying if the trunk lock button could mechanically open the boot. As it is, the microswitch starts the pump. Mechanical override is only possible with the key.

If anyone really understands the working of this gadget, or if there is a thread on this already to point me to, I'd really appreciate it.

Hoping this forum is a bit more technically oriented than the Benzworld site. I've all but given up on that one.

 

[Dec]

First thing to do is identify the Yellow tube that goes to the trunk lock.
Next, remove the tube from the vacuum pump, stick it in your mouth and blow real hard through it, this will/should pop the trunk open, blow through this tube to the lock replaces the blowing from the pump.

One of these here… Plastic Syringe 60ml from Bath Potters' Supplies ... is very good alternative to blowing with your mouth if you can temporarily attach it to the end of the Yellow trunk lock tube with tape to make it air tight.

If you can blow the boot open without the aid of the pump then you can rule out the trunk lock as being the cause of the problem.

https://www.youtube.com/watch?v=UskH0ZZ6GlI

[YOUTUBE]UskH0ZZ6GlI[/YOUTUBE]

Dec

EDIT. See also post #17, here...http://www.mbclub.co.uk/forums/electronics/176504-c200-w202-wont-start-central-locking-broken-2.html

 

[Dec]

A better test of the trunk lock is in the video below.
If you swap over the 3 door lock tubes with the trunk tube you can test the trunk lock with the door unlock button AND test the door unlocking by pressing the trunk unlock button for more than one second.

https://www.youtube.com/watch?v=VTVfLTQ8r_g&feature=youtu.be

[YOUTUBE]VTVfLTQ8r_g&feature=youtu.b[/YOUTUBE]e

 

[roger574]

I've had a similar problem with my W210 E55 since I bought it last March. My mechanic fitted a brand new pump and the boot release would work for a while, both from the key fob and the interior switch, then stop. The central locking was unaffected.

He found that if the power was removed from the pump the system would reset itself and it would work exactly ten times before stopping again. It transpired that the pump was in a fail-safe mode because previously some fluid had got into the CANbus somewhere in the front passenger footwell, hence it working for a fixed number of times.

I'm not exactly sure what he did, but he managed to sort out the CANbus issue at the end of July and the boot release has worked faultlessly since

 

[Dec]

This is a common problem with the boot lock, it not responding to fob or interior switch, I’ve heard also about disconnecting the vacuum pump as a temp fix but you are the first I have heard to mention that the have fixed the fault.

Would you be able to ask your mechanic exactly what was the cause and what he did to fix the problem?

Dec

 

[roger574]

This is a common problem with the boot lock, it not responding to fob or interior switch, I’ve heard also about disconnecting the vacuum pump as a temp fix but you are the first I have heard to mention that the have fixed the fault.

Would you be able to ask your mechanic exactly what was the cause and what he did to fix the problem?

Dec

Perhaps the OP could disconnect their CDL pump to see how many boot release operations it then works for before stopping, then repeating to see if it's the same number?

In the meantime I've emailed my mechanic and will post any response I get.

 

[roger574]

Here's the verbatim reply from my mechanic:

"Boot opening problem might have several reasons. In your car had CAN BUS problem.

Initially he needs to check boot lock micro switch then boot light switch then continuity between switch to CDL pump.

If these all ok then need to check interior CAN BUS. I can't remember at the moment which connectors I cleaned but I will check wiring diagram and let you know."​

As soon as I get any more info I'll post it here.

 

[Dec]

Thanks Roger.

Dec

 

[ronwyer]

Great subject matter everyone, thanks. I am happy to report that this afternoon the boot failed to open exactly one week after I swapped in a different pump. I am going to try the electrical disconnect trick and see what that does.

Roger: You might be on to something there. I am awaiting your update regarding the CAN bus.

This all makes my 71 280SE seem downright primitive by comparison.

 

[ronwyer]

My trunk lock will now work exactly 10 times before it goes inoperative. A power re-set solves the problem! Now, to figure out how to analyze the CAN bus to figure out why it is going into fail safe mode in the first place.

 

[roger574]

My trunk lock will now work exactly 10 times before it goes inoperative. A power re-set solves the problem! Now, to figure out how to analyze the CAN bus to figure out why it is going into fail safe mode in the first place.

Sorry, my mechanic hasn't provided any more information on which CAN bus connectors he cleaned to clear the problem once and for all.

This is exactly the same problem my car had and the boot release, both from key and console switch, is still working.