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.

 

[BlackC55]

Disconnect the electrical connector on the pump for 10mins. See if this helps.

 

[quenching]

Ahh, the old off and on again trick! I spend half my working day getting people to do this and still never remember to do it myself when stuck. Seeing as the pump is a bit of a pain to get to in the estate I presume disconnecting the battery for 10 mins will have the same effect? Thanks for the advice, I'll report back on any progress.

 

[quenching]

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?

All other suggestions welcome!