I got a 2007 Mazda 3 for around 6 months now. It had 1 problem which the door ajar light would flash real fast while driving etc.. but stopped after 1 week. Now 6 months later, the light is on 24 h , i brought my car in for recall mp26c which they install a sashkit etc to prevent premature rust inside doors. How can i prove to Mazda that the damage to doors was probably caused since those pieces were missing because it would cost me 500$ to get doors fixed (door ajar light)? Or how can fix this on my own and were is the door sensor located.

BTW the right front door the unlock and lock switch works sometimes randomly, it will always lock but sometimes does not let me unlock?

 

No matter what corrosion you have in the doors, they won't take responsibility for it. You must live on the coast with salty air, or go to the carwash too often, or leave your windows open when it rains etc...

The door latch is where the switch is, which is the only place it can be to sense when the latch is actually latched and properly turn on the light. I haven't pulled the door apart far enough to see this switch, it's behind the inner door plastic - many bolts and a pain to get off i'm sure. Not to mention I think you need to take the window out to get that panel off.
I'd bet the switch needs to short wires together to make the light go out - so you could short those two wires and just use your ears to make sure the doors are shut.