The drivers door does not lock and alarm sounds when opening the door. The internal lock lever shows that it is locked however. All other doors are shut and locked

 

sounds like a mechanism problem.

just because the lock lever is in the locked position does not mean that the door is locked. it all works on linkages. think of it like a chain, if one link in the chain fails when one end is pulled, the other end doesn't move. so the lever on the door moves, but the actual locking part of the door latch doesn't move.

 

Thanks for that. the previous owner says that there is a procedure to go through to fix this problem but I havnt got the manual. perhaps someone could help?

 

I have discovered the fault. The second remote key works the locks OK so will have to get the old key programmed

 

You might wish to read the 15 page pdf that is one of the files in the link below related to the locking system.

There may be more to your concern than just a problem with one key fob; rarely is a fix that simple.

In theory you can program the fob to open only the drivers door on the first click and then the second click unlocks the other three or you can program that all unlock on the first click but what you have, to me, sounds unusual.

DISCO3.CO.UK Photo Gallery - Power Window and Door Lock Circuits

 

It does sound like the mechanism. Although the lock lever appears to flip in, it does not quite go all the way. You can manually flip it out and in, and the door locks. I ended up replacing the two rear door mechanisms to cure the problem.

as bbyer mentioned, the lock behavior is programmed for each fob, I have one programmed for each behavior (his) unlocks all doors with one button press. (hers) unlocks only the drivers door with one press. An additional press unlocks the remaining doors.