I think you will find the reason it breaks off is because it is tinned a fair way up the wire and so offers no flexibility therefore it acts like a solid strand of a single wire and has no give.
Vibration and movement cause flexing of the stiff, tinned wire and so it snaps.
It really doesn't have a lot to do with the gauge of the wire used IMO more HOW it has been connected.
I feel that most harnesses are inadequately supported with cable clamps etc and wires are just left "hanging in the breeze" this is the main cause of wiring problems as I see it.
Perhaps use 20 or so small cable ties and prevent the wires from flapping about would do more than replacing them?
thanks Mike will try. Always looking for explainations to problems and seeing if they could have been avoided.
