[Mickd]

Oh... and you WILL measure 6v on that sender wire as you found, because you're reading that voltage through the gauge. If you reconnect the wire back on the sender unit, you'll get a lesser voltage reading. Dunno what what, but it'll be less than 6v.

You see, what's happening is there's 6v there as you found out, but because you've lifted the wire off the sender unit, then there's no load presented to the 6v supply, so you'll see the full 6v.

Funny stuff electrickery.