My van came with 3 keys to open various doors and the drivers door could be opened with any key! I have spent the day playing with the lock barrels for each lock now I have a van that has one key that opens all doors and starts the van!!!
I had to replace the rear hatch lock as the incorrect lock was fitted this meant yet another Key so I took the old lock apart and found that it had 6 levers/plates that made up the lock combination, when the key is inserted it pulls the levers in allowing the barrel to turn in the lock. having found this out I thought I would test an idea out on the damaged drivers lock, as I had nothing to lose. The barrel is removed by punching out a small roll pin this allows the barrel to be pulled out from the handle, its easier to do this with the key inserted as it stops the levers from falling out of the barrel. Insert the key you wish to use in the lock, you will find that some levers remain sticking out and some will be pulled in these are the correct levers.
By withdrawing the key slowly to the first lever sticking proud I removed the lever and swapped it with one from the extra lock I had, I did this until I found a lever that when the key was inserted in was pulled in as the others, this did not take long about 2 attempts when complete I moved on to the other proud lever repeating the previous actions, I then reinserted the barrel into the handle and replaced the roll pin(removing this and replacing is the hard part).
I attempted to use the other keys and only the one I set it up on worked!! so at that point I had a Van with one key that worked the ignition and one door. Next I had a go at the passengers door using the same method of trial and error replacing levers I again ended up with a Lock that operated with the same key as the ignition.
The Side door came next I have the long handle type, the barrel is held in place with a small screw this removed allows the barrel to be removed there is a spring at the base of the barrel which you must not lose, by using the same method this too was adjusted to fit the ignition key, when rebuilt and fitted I had 3 door and ignition off of one key!!! The rear hatch was done in the same manner its barrel is held in by a small roll pin and it was adjusted as easily as the others. All locks were oiled and greased where required and tested with various spare keys to ensure they would not work on any other key except the ignition key.
All in all a good days work I now have a van with 2 keys one for the filler and the other to open the doors and start. As I said I might have been lucky to have found the correct levers so I can not guarantee it will work on everyone's lock but I'm chuffed as its saved me many pounds
T4 Karmann Colorado