reversing light switch

If you ever have to change your reversing light switch be aware it will need a washer or sometimes two to work as a spacer.a washer should be supplied with the switch but not always and if thats the case theres nothing to indicate its essential. The washer is necessary as a spacer because without it the switch is too sensitive which makes the reversing light stay on permanently.
That happened to me and of course i only realised after getting the car off its axle stands and putting away all the tools. After removing the switch and trying it on the bench I worked out it needed a spacer and luckilly had a spare oil drain plug washer to hand that was the just the right size.

Naturally the next day I found the original washer that had fallen off without me seeing it when the old switch was removed.

I suspect that you could go down the transmission tunnel in any one of our cars & with a strong magnet collect, in addition to some rust any number of stray pieces of hardware.