Interesting!
So, based on that, there SHOULD be a full 12v at the changeover switch???
It's such a pain having to keep tabs on mileage and physical checks on the level in the tanks.
As far as I know, yes. Conveniently I'm in the US with the ambulance (a '66 with changeover switch) at the moment so I'll stick a meter on it to double check. Poor spades, dirty connections etc don't help. Last week's trip from Montana to Idaho had one tank reading full all the time, wierdly that was a dirty/poor connection to the sender. I'd always assumed that would give an empty reading but seemingly not.