I've now had a chance to look at the wiring for your car.
First thing to establish.
1. Does the car unlock both doors
with the key in the driver's door?
2. Does the car unlock both doors
with the key in the passenger's door?
If the answer to both
these statements is yes, then the central locking controller ( N11 ) is unlikely to be at fault.
The way the car is wired ( according to the manual ) is that when either pin 2 or pin 3 of N11 connects to ground ( car body ) by way of the key locks it either locks ( pin 3 ) or unlocks ( pin 2 ) the doors.
To confirm N11 is working correctly :
1. Find N11. According to the manual, it is plugged into the main fuse box towards the bottom ( when the fuse box is swung down ) on the left hand side. It is a large device roughly double the size of the other boxes ( relays ) plugged around it.
2. Pull it out and look at the connector side. There should be two groups of 3 pins each arranged as a triangle ( 4 pins along one long edge and 2 pins along the other long edge ). With the 4 pins at the bottom, from left to right you have pin 3 and then pin2. Look carefully and you may be able to confirm this from numbers moulded into the plastic. Put N11 back in the fusebox. Find connector 'L' on the wire side of the fusebox. Each connector should have it's designator moulded into the plastic. Pin 2 of N11 is connected to Connector L pin 4 and pin 3 of N11 is connected to pin Connector L pin 3. Again, to help confirm, N11 pin two should have a white wire connected to it and N11 pin 3 should have a Light Blue wire connected to it. If you download the workshop manual, look at the file named 'Repair Instructions Vol 3.pdf' ( NOT part 2 ). Find Section 55-20 page 5 and it has a drawing of N11 and on page 4 it shows you where N11 is on the fusebox.
3. Get a piece of wire and connect one end to a known good earth ( e.g. the body of the cigarette lighter ).
WARNING : Be absolutely certain you have identified the correct position of pins 2 and 3. Most of the fusebox is connected to battery + and the following tests could be catastrophic if you get it wrong.
4. Check it again!
5. With the doors shut and unlocked, momentarily touch the other end of your test wire to pin3 of N11 ( car's light blue wire ) by pushing a bare end of the wire into the receptacle with the light blue wire. The doors should lock.
6. Now, in the same way, momentarily touch your test wire to pin 2 of N11 ( car's white wire ). The doors should unlock.
If this works, N11 is not the problem and if the key works in both door, I don't think it is the problem.
The remote control works through the car alarm and for the locking/unlocking it merely does what you just did - grounding pin3 or pin 2 of N11 as appropriate.
Further steps of resolution depend on what alarm you have fitted to the car but my guess
at the moment is that you have a non factory alarm ( normal on phase 1 I believe ) which may be a Scorpion 918U and that there is an intermittent bad connection between N11 pin 2 and the alarm system.
Let me know how you get on and describe your alarm remote for me. Guess : It looks like the one in the picture here : http://www.alfaowner.com/Forum/alfa-...ml#post3337600
Updated : see point 2 for correction