My Disco (97) has developed, what I'm assuming is, an earth fault.

When I press the foot brake the headlights come on, when the lights are actually on the brakes when pressed do work but tbh its hard to tell that they are.

So far I've isolated it to the passenger side - with that light cluster unplugged no flashing headlights. Both clusters have been taken out and cleaned up and all the bulbs checked so now I'm looking at the bumper lights though they appear fine as well and unplugging them makes no difference.

Anyone any suggestions whereabouts to start looking or is it just easier to cut the existing earth on that side and run a new one to the lights and the earth at the front (passenger side footwell??)?

 

For testing I'd just use a length or wire or a battery jumper cable. Start by jumping negative battery to the truck frame. Then repeat to the engine block. Then the headlamp area. You may find the missing ground link by this substitution.

BTW, the negative battery lead snakes down beside radiator and ties to frame, and other spot to clean up and tighten.

 

Thanks SB.
Earths cleaned up and a series of jury rigged wires from the connection block and a good temp earth later and I think I've narrowed it down to a short on the left side high level tail light.

Bumper lights and right side are unaffected so I may just look to run 2 new stop and tail wires from the right side and bypass the leaking electricity.