I know there was a similar thread a little while ago (but this is different!)
I'm re-wiring the boat just now and including a fuel gauge. This is wired as shown below (hopefully) and is exactly as shown in the vetus wiring diagram.
At the moment, because there's no engine on the boat yet, most of the loom is unconnected.
Rather than have the gauge lights on all the time - ie permanently ingnition powered - I'm wiring them to come on with the nav lights. However what's happening at the moment is that when the nav lights are switched on, the needle on the fuel gauge goes all the way to full (tank is completely dry) and stays there.
What I don't understand is how supply to terminal 1 (on my photo) is getting to terminal 5. As the only connected earth is via the sender unit, I'm having to assume that's how the current is routing.
Terminals 3 and 2/4 are unconnected.
The sender itself has two wires coming from it (blue and brown) and the instructions say it can: be fitted with minus to earth or unearthed (two pole)." I don't really understand what two pole means, so I've done it with a 'minus earth'. I'm assuming it doesn't matter which of these blue/brown wires is supply and which is earth.
Any help appreciated. I'm a bit stumped otherwise. Is this to do with the 'two pole' option on the sender and would it be resolved if an earth was connected to terminals 2 & 4??