Temp light and Rev counter go nuts when I turn headlights on

Hi guys,

When I switch on my headlights the red temp gauge warning light flashes on and off constantly and the rev counter needle starts jumping all over the place, but when the lights are off it doesn't happen. What are the main things that could cause this?

Thanks,

John

Is it a gti? There should be a brown white wire that goes to the rocker cover, then an earth braid strap goes to the coil mounting bracket bolt.

This is the main earth for the dash clocks.

Yes sorry, it is a 1984 cabriolet GTI. So it's likely that this brown earth or ribbon isn't connected properly or broken somewhere along the line?

It's a possible solution.

First look at the brown/white stripped wire. This goes to the rocker cover corner stud. There is usually a plate, from there a braided earth strap goes from that plate it goes to the coil mounting bracket bolt.

Another issue is a poor connection on the back of the clocks.

Ok, thanks chortle, i'll take a look and post how it goes!

I had a quick look for the brown wire at lunch time so I knew which one you meant but only moved it round a little bit to see where it went. On the way home the problem had magically gone away! Now it's a bit of a coincidence as it has been a consistant problem for months! Hmm, just have to wait and see if it comes back, may try and check all the earth wires and contacts properly.

Cheers,