Dashboard switch, 1 or 2?

On my 1982 cab i have a circular yellow switch inset in the top right corner of the dash, the two options for this are 1 or 2, it has no effect on the lights, i have no idea what this does, nor did the previous owner, if anyone knows what this might do or any ideas at all it would be great, thanks.

Have you got a trip computer? if so watch what it does when you twiddle your end :-)

cheers, i thought it mite be linked to that, it doesnt work though, the computer is just stuck on the time. thourght it might be to switch between km and metres.

don't you have a little button on a stalk that cycles through the functions?

I might have one in the garage if you actually have the correct wiring loom and somebody hasn't chopped off the connectors, they would be really thin wires coming out of the ignition switch loom, you do have a rev counter don't you?

yeah there is a button on the end of the right hand stalk, it doesnt work though, im unsure why. and i do have a rev counter.