Wiring....again!

[ScoupeS12]

My 12 has a new issue now. Which one of you guys may have come across before, so I thought I'll ask before I start going multimeter crazy!

Occasionally when I am driving her, the rev counter just stops working (drops to 0 and then springs back up to where it should be again. And then not always at the same time, the clock stops working. However that can be from a few seconds to a few minutes.

Also the other day I started it up and the rev counter didn't work at all, and the boost gauge just sprange all the way to full...and then at the same time the rev counter started working, as did the boost gauge.

So if no ideas, no worries, but if so might help me at least look in the right direction!

Cheers.