w168 central locking door problem

[Deletedmember18260]

Hi folks, signed up years ago when I had a c220 cdi. recently purchased an a140 for my wife to run around in and its a brilliant wee motor except for this 1 weird problem...

In the merc, if after you unlock the car, and you do not open a door within 15seconds (i think) it re-locks itself and arms the alarm. If I open the passenger door it doesn't seem to recognise it and locks/arms itself again. Similarly opening the passenger door does not activate the interior lights.
The door locks and unlocks fine tho which is whats puzzling me.

I've checked (but not replaced) the little door switch in the door shut and its physically operating fine but I haven't opened anything up yet till I know what to look for.

So, any help in what might be the cause?

It's led to the keys being locking in the car twice now at a cost of £70 then £60 to retrieve them from a locksmiths. (We have no spare key.)

 

[Dec]

In the case of my W202, if the car is unlocked with remote fob but no door is opened within 40 seconds then the car will relock, that’s normal and is probably applicable to your car too. The idea is to counter accidental unlocking with the remote fob.
It might or might not be possible to have this feature turned off with STAR diagnostic.

One solution could be to buy a spare metal key blade and conceal the key blade on the body of the car for retrieving the locked in keys.
Opening a door with the key blade, while the car is locked and alarm armed will set off the alarm… retrieving the remote will enable you to unlock and disarm the alarm, a lot cheaper and quicker than a locksmith.

Maybe the car has a light sensor which disables the interior lights during daylight hours?

Dec

 

[Deletedmember18260]

Hi, thanks but the problem is not the auto lock, it's the fact that when I unlock then open the passenger door, it locks again because it hasn't detected that the door is open. Likewise the interior lights come onwith any other door but not the passenger door.
Just wondering if anyone knows if there's a fuse or switch specific to the passenger door I can check?

 

[Dec]

The door locks are vacuum operated, air is sucked (vacuum) from the lock actuator to lock the door… door pin moves down.
To unlock the door, air is blown (Pressure) into the lock actuator to unlock the door… door pin moves up.
.
To get the passenger door to lock you would have to disconnect the Yellow tube that goes to the passenger door lock, this would allow you to lock the passenger door manually for the time being.

The Yellow tube, that goes to the passenger door, that you disconnect MUST be made airtight and the point where it was disconnected would also have to be made airtight with, maybe electrical tape.

Alternately you could disable the vacuum pump by removing the fuse for the vacuum pump or unplug it if you can’t find the fuse, you would then need to manually lock the car with the metal key blade in the door.

Vacuum pump w168 = A140… Bert Rowe's-A-class info. Vacuum Pump (central locking)
Also… Albert Rowe, Lofty's homepage

Dec

 

[Deletedmember18260]

Hi, thanks again for another detailed reply, as above tho its not a locking problem - the door locks and unlocks fine. The problem is the passenger door does not seem to register when it is open. I.e. Interior light not on, car locks itself again when unlocked. Whatever happens in the door mechanism to say it's open, is not happening on my passenger door. I've already searched loftys site to no avail.

 

[Dec]

Sorry, I’m misunderstanding you .
The door pin switch has nothing to do with the door locking, its purpose is to turn on the light for the passenger and to tell the alarm that a door has/is open.

If the door locks and unlocks ok then the only problem you have is that the light is not coming on when the passenger door is opened, perhaps a faulty door switch or dirty connections at that door switch.

Another consequence of this fault is that if a thief broke in through the passenger door then the alarm would not go off if the door switch is faulty.
It might be a good idea to test your alarm system, see… http://www.mbclub.co.uk/forums/electronics/169666-w202-how-test-car-alarm.html

Dec