I tired to repair the inertia locks on my seat belts and finally gave up and bought new. When I took the ratcheting mechanism apart what I found was amazing. There is a marble seated in a depression on a piece of sheet metal that appeared to be cut from an old biscuit tin with paint and lettering on it.
I never could get the old one to work correctly and considering on most drives I'm reminded that my ear is about the same height as the wheel hub of an SUV I thought replacement was due.
The new ones work great. I think I'll disassemble the old ones for pictures and post them.
I had mine out when I installed the new carpets. While fooling with them they didn't seem to work so I disassembled them and fooled with them some more, gave up and reinstalled them. Once bolted in and the mable settled into the bisquit tin, all was well. It wasn't what I was expecting either, but it does work. Sort of like the inertia switch on some fuel injected cars.