Several years ago, the spring included in my door lock broke, so the door handle was always down, and the lock kind of open...
So I decided to proceed to the replacement of that broken spring. But I was not able to find the part on the internet, so I tried to make it by my own and the result is quite satisfying and really reliable (It has not broken down in a year...)
Step 1: Open the Door Lock
First of all, we need to take away the lock from the door and to open the mechanism to identify the problem. As it was a 5-point lock, it was quite long to do it.
Step 2: Find the Good Wire
Then we need to find a steel wire that will not deform plastically, but will keep the geometry needed. I decided to use the steel from a hub cap that I found on the roadside.
Step 3: Cut and Shape the Spring
Then, with a plier like this one, you will be able to shape your spring. Take care of the initial diameter of the spring, and the number of loops of the wire, if the new spring is too thick, the latch will not work properly.
Step 4: The End
Now, you need to adjust your system by testing its working. In my case, I needed to put the lock back on the door and make some tests. But everything was working properly, the handle is now a little bit more hard to press as before but it stays up!
I think that it is possible to make something similar with a "cheap" steal wire not working as a spring, by making a thermal treatment on it (quenching and tempering). I made something similar for the spring of a folding knife.