Shortly after buying my car I started to have problems with the driver's side door lock. Using the keyfob would lock the passenger side door and set the alarm but the driver's door could still be opened.
I tracked the problem down to the door lock solenoid, the problem was intermittent and could be temporarily resolved by 'jiggling' the actuator. This would make it work for the next couple of cycles.
I checked the wiring and it seemed to be basically sound, I also checked the door open/closed switch but this was working fine.
A replacement solenoid can be sourced from Maplin. There are two types, a two wire (part number: YD79L) and a five wire (part number: YD78K). They cost about 9-10GBP each. The one I wanted to replace was the 5 wire version.
Replacement Process
The solenoids are mounted in a frame within the wing, behind the door. You can access this area by lifting up a carpet flap secured by velcro. Inside you can see 2 solenoids, one to open the door and the other to operate the lock.
To remove the solenoid you need to loosen the frame. To do this just remove the 3 allen bolts in the door gap. The frame can the be rotated to give access to the screws holding the solenoids in place. Mine was slightly stuck with sealant but it came out okay with some gentle persuasion.
Once the new solenoid is in place (don't forget to re-attach the actuator arm), you can replace the frame. Be careful to try and get it back into the same position so that the door shuts cleanly.
Wiring
The solenoid I replaced was the 5 wire version, here's a table of the wiring that worked for me. It did take a bit of trial and error to get it right as the wire colours didn't match up.
Car
Old Solenoid
New Solenoid
White and Black
Brown
Brown
Grey
Black
Black
Blue
Red
Blue
Red & Blue
Blue
Green
Note that both the old and new solenoids had one spare wire which was just taped off.
