Tachometer/rev Counter Irritating Electrical Fault

Triumph bonneville t100 2015
Has anyone else had a problem like this one?
I need advice or help on a problem with my tachometer. The needle randomly swings all the way over to the right and all the warning light's flash on and off. Now when I turn the handlebars to the right the light in the tachograph goes out. This doesn't affect how the bike runs. I have the tank off and it appears as though there is a little damage to the harness where it has been nipped up under the tank but nothing obvious.
Where on earth would i start with such a complicated looking wiring harness

Thanks
David

 

Thank you everyone. I think I might have identified the problem. As mentioned by 'the
Mighty Boosh' it is probably the stretched harness. I took the headlight shell off and loosened all the harness and all seems well. I don't know if there is any permanent damage but the tachometer is working great now. I will see what happens when I put it back together taking care not too stretch it or squash it up in the headlight shell.
Thank you everyone
David