Electrics not behaving

[JT]

A mates honda ascott is having some funny problems. Its an auto '90s something.

When you apply the brakes, moving or not, the dash display does will intermittently do funny things. The engine temp gauge rises fast, and if you indicate, the needle will pulse. The stereo and heater sometimes cut out, as does the rev counter and speedo. Engine still runs fine though. Battery voltage off and on are fine

I thought its probably a short in the brake wiring, a quick check revealed nothing. All brakes lights still working fine. I've checked all the connections in engine bay. Any ideas whats causing this?

[Alex B]

Sounds like a poor earth to me