central locking, all exept one

Easy fix is to get some silicon spray/wd-40 etc and spray around the lock so that it will run down the lock. Give it a really good spray. Sit in the car with the remote and keep locking and unlocking the doors. As you lock the door, put a little bit of pressure on the lock to help it. If it does go down with a little bit of help, you know it is at least partially working. Help it out a couple of times and eventually it will start to lock without help. Sometimes you just have to wait until the next day so that the lubricant has time to work its way down.

This will fix it, maybe for a year, and you will probably have to do this again when it starts playing up.

Better fix would be to pull the door trim off, lubricate all the moving parts and check for parts that are causing the problem.

 

In addition to Kopper69's advice, check the power wires to the door where they exit the B pillar and also where they connect to the lock solenoid. Strange how its generally the left rear door that gives trouble.

 

So the back left one unlocks okay but wont lock? Or it's not working at all?

When I got my car, I found out one of the locks wasn't working at all unless I did it manually. Put up with it for a bit, till I got sick of accidentally leaving the back door unlocked. Popped off the door skin & found out that the previous owner have chopped out half the central-locking loom. I can't for the life of me figure out why someone would do this. In fact I found a ton of things that the knob tried to jerry-rig & cocked-up.

Some people shouldn't be allowed to reproduce, but I digress ... I ended up replacing the loom. Cost 20$ & took 15 mins.

- I suggest getting the skin off & having a good look.