Central Locking issue - Not a key fob

[trueblue76]

Hi all, new to this site as I have just bought my first Ford!  OK so its a really old 2000 Focus but that's what I could afford.

I have had to do some small bit of work to get it past the NCT but I am now looking at fixing an annoying central locking issue.  There is no remote locking on this model it is just the standard torch key type key.  When you lock/unlock from drivers door, the central locking does not work at all it only unlocks the drivers door.  However on passenger door it is very intermittent.  In the 1 month I have owned the car, it must have worked about 3 times unlocking all  doors from passenger side.

Its so annoying because I now have to take the key out of the ignition every time to open the boot as the release button does not work when the central locking is not operational and I have to manually unlock all doors from inside for passengers.

I suspected the fuse at first as it was not working at all, but then when it worked intermittently from passenger door I discounted that.  Is there anywhere I can start to fault test on this?  It must be a sensor or switch somewhere that is not working.  I am not even sure if the alarm works because the "double locking" does not seem to work as per the manual and there are no flashing lights when I lock the door, although the tiny internal red light flashes after locking up.

Any advise is greatly appreciated.  Thanks.

[trueblue76]

selfless bump.  

I'm guessing no one has any knowledge of this due to lack of replies.