Fixing a Mazda Miata MK1 car lock
I can't even remember if the passenger side door lock ever worked when you inserted the key. It wasn't until my recent road trip I discovered how annoying it was not being able to lock the passenger side door from the outside. With my recent interest in lock-picking and having seen many videos of locks been taken apart, I thought it was about time to tackle this challenging problem.
First was the matter of getting the lock out of the door. Luckily somebody made some really good instructions (see here). Most people seem to replace the locks on the car, but I was all up for restoring it. After carefully taking the lock core out of the bible (housing) I could properly check what was wrong. NOTE: be careful not to loose the tiny ball bearing used to index the resting position of the core in the bible when taking the two apart. I am now pretty sure that somewhere in in the last 27 years someone has tried to open the lock by jamming a screwdriver in it and forcefully trying to turn the core.
The effect was that now the first wafer was permanently stuck and thus preventing the opening or closing of the door by key. After taking all the wafers out, make sure you remember the order, first up was the cleaning of the bible, core and wafers. The wafers can be polished with very fine sandpaper. You will discover a number on each wafer, which you could write done in case you want a new key made.
When attempting to put the wafers back I found out that the first one still didn't move freely. The forceful attempt to open the lock had caused a burr in the core. After sanding that off and removing all other damage I could find it was time to carefully assemble the lock again. And behold, I have a working lock again. Getting it installed in the door is another challenge. Just take your time and follow the instructions in reverse order.
George Timmermans, Research Toolmaker, Software Engineer and Tinkerer