W124 central locking problems - advice needed please!

[quenching]

My '94 E220 W124 estate has started to have central locking issues today. When opening the drivers door with the key (no remote locking) only the drivers door opens, none of the other doors or the tailgate unlock, however if I keep the key turned all the windows will lower as expected. If I open the doors from inside the car and then lock the drivers door, either with the key of by pushing the button down, then all the doors and tailgate will lock. Also if the key is kept turned then all the windows will raise.

I've changed the fuse, even though there obviously wasn't anything wrong with it! And the vacuum pump must be working if it locks the doors. A few months ago I had to swap the drivers and passengers locks around as the drivers one wouldn't turn (now the passenger one is the dead one) but its all been fine since. The car was in the garage yesterday to have the exhaust checked for leaks and they did poke around under the bonnet checking the manifold but I don't think thats likely to be related?

I'm now down to one lock that opens and having to open other doors and the tailgate from the inside, not an ideal situation obviously. Any pointers on what to check next would be very much appreciated.

 

[television]

It sounds to me that you have a vacuum problem and a pipe off or diaphragm ruptured, does the pump run when you unlock

 

[Stedan 126]

Do all the doors lock and unlock from the passenger and tailgate lock, and is the alarm an after market one?

If not, then i'll side with Malcolms diagnosis.

From my old days as an alarm installer, we used to find that if we connected into the central locking feed on the drivers door, occasionally, the alarm fob would not lock and unlock the car, but the key would operate the locking on the boot or passenger door lock.
We found that by disconnecting the power to cdl pump and then reconnecting after a few minutes usually cured it,
The other option was to disconnect the after market alarm CDL connection on the drivers side, and move the connection to the passenger side. Don't forget to join the cars original wiring back together. it was either a blue or green wire.

Its been a while so i may be a bit rusty.

Hope this helps.

 

[quenching]

Thanks chaps, passenger and tailgate lock are both long dead (can't turn the key in them at all any more), there is an aftermarket alarm but I don't have any remote for it and I doubt its been used in years. I've been told elsewhere also the disconnection power to the central locking pump for 10 minutes and reconnecting may do the trick so thats the plan for tomorrow. As the pump is awkward to get to in an estate I'm just going to disconnect the battery and see what happens. Hopefully that will do the trick as I don't fancy checking the all the vacuum hoses from the pump and I've no idea how to even think about tackling a diaphragm problem.

 

[television]

To save you that trouble there will be nothing gained in disconnecting the pump it has no memory at all

 

[Dec]

If a W201 lock is the same/similar to a W124, take a look at the link below. Getting the lock working properly could be the solution to the problem.
http://forums.mercedesclub.org.uk/showthread.php?t=62486

It will be worth checking the connections at the vacuum pump for signs of corrosion, check that the connection plugs are ok, it will be similar to a C Class one pictured below.
Dec

 

[quenching]

As predicted by Malcolm I disconnected the battery for an hour this morning and when reconnected I still have the same problem, doors will lock but not open from the drivers door lock. I can hear the vacuum pump switching on when I lock the doors, it stays running for about 2 minutes then switches off. However, when the drivers door lock is opened I can't hear the pump switching on. Is it that the pump isn't getting the signal to activate or that its getting the signal but not working properly (I presume it doesn't do the same thing when opening the doors as when closing, or does it?)

I can still open and close all the windows from the drivers door lock. I removed the lock and the shaft that turns with the key has a wider end which would appear to activate something inside the door when turned, a switch of some sort I presume? Anyone know what this is or how it works?

Thanks for the door lock repair link Dec, I'm going to remove the passenger door lock that stuck a few months ago and see can I get it working again and while thats soaking in petrol I'll get at the central locking pump and check connectors etc, thats my weekend taken care of

All other suggestions welcome!

 

[Dec]

When you lock the car you engage a switch in the lock which makes the pump run for 5 seconds in one direction, it sucks air through the Yellow tubes and locks all the doors and boot and fuel filler flap.
That bit is working ok but the pump shouldn’t be running for 2 minutes, it should be only running for 5 seconds or less HOWEVER if there is an air leak in the system then the pump can run for about 20 seconds…you might be wrong in your estimate of 2 minutes?

To see if you can detect any air leaks, listen at each door and boot and fuel filler flap for a hissing noise while someone locks the car?

When you unlock the car you engage a switch in the lock which makes the pump run for 5 seconds in the opposite direction, it blows air through the Yellow tubes and opens all the doors and boot and fuel filler flap. That bit is not working so either the connection at the door lock switch or at/in the vacuum pump is where the fault is… the vacuum pump is easiest to check first.

Getting the passenger door working properly will aid diagnosis of the fault as the passenger door …I think… should also lock/unlock all doors too.

Below, my own vacuum pump as an example, not in the best of condition, but working ok, note 1 and 2 at bottom of picture and a bit of corrosion to the right, just stuff to be looking out for.

Dec

 

[quenching]

Thanks Dec, advice and photos very much appreciated. I've just spend the last hour getting the passenger door locking working, I had to remove 4 of the "pins" to get the key to work smoothly and be able to turn it. I can now open the driver or passenger doors with either of 2 keys (I was down to 1 key working in only the drivers door, so at least an improvement in that area).

Both sides will now operate the central locking pump to lock all doors, but only the door the key is used in will open. Both sides will raise/lower all windows. I can't remember if the passenger side door lock should open/close all locks via the central locking or not, at the moment its locking everything so I presume it should also open everything.

Its tipping down with rain here at the moment so I can't hear any air leaks anywhere, hopefully the weather will be better tomorrow. It would seem that the problem lies at the pump end as both doors now do the same thing, getting at the pump in an estate is a proper pain in the backside but it seems it has to be done!

I'm fairly certain the pump runs for a lot longer than 20 seconds when locking the doors but I'll actually time it and see. Its too dark any wet here now to do any more so it'll have to wait until morning.

 

[Dec]

It would seem that the problem lies at the pump end as both doors now do the same thing,

Agree with the above, it must be the pump alright, pay particular attention to the electrical connection plugs that go into the pump, like my pump, yours too is in a “dry area” but it can still have bad connections due to corrosion or broken solder joints.

Get someone to repeatedly unlock with the key while you “maul” or wiggle the pump and its electrical connections… might help to show up any bad connections.

Dec

 

[television]

Do take car with the pump,, when the vacuum circuit is all complete and good, the vacuum controlled switch built into the pump turns it off with a few seconds.

In the event of a leak, the pump will run to the max 18seconds on the electric time built in, if you keep doing this it will burn out,normally a broken pipe or a door lock diaphragm ruptured

 

[quenching]

Howling gales and torrential rain prevented me going anywhere near the car today! I'm sure my pump runs longer than it should, I'll try again tomorrow and report back.

 

[MERC210]

Re pump

I THINK I HAVE A PUMP I BROUGHT IT ON THE NET A FEW YEARS AGO FOR MY SLK BUT ITS WRONG FOR MY SLK ,LET ME KNOW IT YOU WANT ME TO DIG IT OUT IT COST ME £100 THEN BUT IF ITS ANY GOOD I CAN DO A DEAL E MAIL MEIF INTRESTED colin1417@yahoo.co.uk cheers :lol:

 

[quenching]

Thanks for the offer MERC220, I'll keep it in mind if I need to replace my current pump.

During the week the central locking failed completely, doesn't open or close any doors now, and no sound of the pump running at any stage at all. So today I had a poke around at the pump, the 3 pin connector seems to be getting 12V when the door locks are turned one way or the other, tried each pin combination with a test meter and the voltage switches from 0 to 12V when the key is turned. Also I put 12V across the pins on the 3 pin socket on the pump, not a sound out of it with any combination. I removed the pump and took off the cover and found a burnt section on the circuit board, also smells of burnt plastic a bit.

Is it worth resoldering the burnt out section on the circuit board? I can't try this until Monday.

Is the second socket on the pump for power? The one under the 3 pin socket below. I never though to check if this was getting any power when I had everything apart Is the 12V on the 3 pin socket just a switching voltage to signal the pump and it draws power from the other socket?

In case its of any relevance my pump has the following printed on it....

Thanks for all the advice offered, it really is appreciated, its great to have others expertise to assist my very limited experience.

 

[dieselman]

It is worth trying a repair, but be aware it may be the motor brushes causing overloading of the circuit board.

 

[Dec]

You have found the source of the fault alright, the question now is why did it burn like that and why did it not blow a fuse.

Don’t know too much about soldering but in the absence of any other advice I would solder in a piece of insulated wire so as to bypass the broken track, others may advise better than me.

There is a coat of protective Varnish? on the PCB, that is possibly the cause of the smell, electric motors also stink too when the burn out.

Close by your vacuum pump you will have a Comfort Control Unit like below it should be wired to the pump via one of those connectors, The Comfort Control Unit handles window opening and closing.

Is there a bad solder joint at White arrow in attached picture?

Dec

 

[Dec]

This might be of interest as it looks similar to yours, note the motor is replaced rather than trying to replace the motor brushes which are at the opposite end of the motor.
http://www.youtube.com/watch?v=9MkpUtLwPN0

See also… http://forums.mercedesclub.org.uk/showthread.php?t=71538


Dec

 

[television]

From my experience on working with these pumps one of the diodes will have gone short circuit causing the track to blow, I can try and fix it if you wish or its a new pump.
I did warn that you had a vacuum leak and that this would happen if the pump was running all the time till it timed out

 

[quenching]

Thanks gentlemen, I'll try a quick fix of a bit of resoldering on Monday but I'm assuming that even if I fix the pump, or replace it, that if I have a vacuum leak somewhere its only going to cause the same problem again. Although at least I'll get a chance to hear any hissing leaks if they're there. If the soldering doesn't work it'll be a replacement pump I'd say, I can source a secondhand one for about €50.

Seeing as you mention the Comfort Control Unit Dec I've also lost the ability to open/close all the windows via the door lock, so I assume my dead pump has also either killed the CCU or just not sending the relevant signal to it any more.

Thanks for the repair offer Malcolm but I'm in Ireland and its more hassle than its worth to ship it to you and back. I did tell my wife not to use the central locking as the pump might burn out and she swears she didn't, who am I to argue with that! It was obviously on its way out anyway if it was only working in one direction so I can't complain too much.

I also have a 1984 W201 that uses the same type of pump, if the part numbers match up I might swap it to rule out any other potential causes but it has an aftermarket alarm that also operates the central locking and I'm slightly reluctant to mess with at all.

On a positive note the W124 did its NCT (MOT equivalent) on Wednesday and is now road legal until April 2013!

 

[Dec]

As of now, you don’t know for sure if you have an air leak or not and you don’t know if the pump is broken or not, all you have is a broken track.
You can test the pump independently of the car with a battery charger… you seen your man in the u tube video running the pump, in one direction it will suck and if you reverse the polarity it will blow… that is if it is in working order in both directions.

You have 6 Yellow tubes going into the pump, you can test the 4 doors, boot and fuel flap for an air leak by removing each Yellow tube from the pump and blowing or sucking it hard for about 3 seconds.

To find which one is leaking, if any, pull off each tube and blow or suck hard through that tube, the door/boot or petrol flap that corresponds to that tube will unlock when you blow or lock when you suck, the one that doesn’t lock/unlock is the one that is leaking… if there is a leak.

When you blow you unlock…when you suck you lock, just like the pump. You will be able to hear each door etc lock or unlock.

The pump is connected up to the CCU so it’s to be expected that the windows aren’t working as before. I wouldn’t mess with the W201 as you can really find out what it is you need to know as suggested above.

Dec