how can i fix the locking mechanism on my ford ka1998?

1 of 2 things.....

1. the exterior handle is broken behind the door skin - this can nornally be identified by shaking the door vioently a few inches either way and u normally hear the metal rod loose where it should be connected to your handle

OR

2. your key/lock barrel is too worn to work properly. this can be identified by when locking with your key the door WILL lock but will NOT unlock. just look at the interior handle for movement for verification.

hope this helps!

both common faults......

Mark - loughton.
October 2009