Fuel gauge/light switch

[Scuba bug]

Don't you just love 47 year old wiring...
Out of the blue, every time I turn the lights on the fuel gauge flies over to read full, same with main beam switch...any ideas? I've checked connections, looked for bad earth etc. It's doing my head in!
Could it be the switch or the relay..

 

[sparkywig]

Bad earth, check dash pod earth and high beam relay.

 

[Scuba bug]

Sorted, bad earth at the back of the cluster, had the dash pod out and cleaned all of the terminals and connectors, happy days..