Strange happenings in Dashboard Electrics.

[124cso]

Out of the blue, I have developed an elec fault/s. 86 Air cooled with later BIS type oblong dash panel.

Turn on park lights or headlights and petrol gauge zoomed up to superfull. Now it appears petrol gauge has stopped working at all. When I turn on park lights, indicator/display lights come up for fog light, rear window, hazard, high beam. Indicators work but no flasher light on dash. Turn on rear window and high beam and those display lights go off !
Fuses are all o.k. I have not been playing with any wires (recently) so I suspect a short or wire damage somewhere but not sure how all these are inter-connected ??

[ChrisRLewis]

Sounds like a connection or earth problem.  I would check out the 3 sockets on the instrument panel first, clean the sockets with contact cleaner.
If still a no go concentrate on the fuel gauge circuit, it's a simple circuit which will hopefully give you a clue to the main problem.

[eben80]

Check the earth wire at the fuel tank. This made my gauge show full all the time..

[124cso]

I'm pretty sure I have the problem solved.
I think I can put it down to corrosion on the common earth tab connector/s on the printed circuit board which forms the basis of the dashboard. Fairly easy to clean up the board tabe but cleaning the small connectors inside the plastic plugs is a bit more challenging !