Stuart,
You are correct in your first paragraph. As for the restoration, to my knowledge the system was fully 12v except for the starter which was converted during the restoration. There is a metal strap that goes from the gauge to the dash (not painted) that is broken which I think occured when the mechanic installed the oil pressure line to its gauge. I think someone told me I was to ground the sender which I did from one of its mounting bolts to the battery neg terminal(should be a good ground?)Assume that's not a good enough ground and that the gauge also needs a ground. What about reversing the wires on the gauge, should I put them back? The gauge does move when the ignition is on so it's trying to move which makes me think its ok.
John
