Help Fuel Sending Unit

[Slow and Stubbor]

Can anyone offer any advice? The guage is original. This is not an original tank or sender. It was a resto 20+ years ago. Meter on the sending unit gets 90+ ohms full and 2 ohms empty. Guage reads EMPTY with no leads attached. Hooking jumpers and 12v to the gauge and sending unit gets a FULL reading at all float positions, no change with changes in float position. Bad gauge?
Thanks

[Tom Petroff]

Would help to state the year. Gauge and sending units greatly varied over the years especially early years.
And if your applying 12V to a 6V gauge it's toast.
TGP

[Slow and Stubbor]

Thanks for offering help. I don't think the year really matters in this case. The truck is a 1959 and an original 12v truck. As I said the tank and sending unit are not original and not PW. There are no markings at all on the sending unit to offer any clues as to what or where it came from.

[gmharris]

Well it sounds like the gauge works, at least at the full and empty positions. The sender seems to work based on your resistance readings. So, that leaves either improper connections or wiring.

Based upon your report that the sender reads only 2 ohms in the empty position, the gauge should read empty at full voltage. You said the gauge reads "full" at full voltage. Hmmmm?

I think most gauges would be designed to read "full" with the higher voltage. But, I don't know if this is true with all gauges.

Sounds to me like the gauge is getting full current. Probably because it's wired wrong. Is it a one or two wire system? That makes a difference where the current is introduced into the system. Time to look at a wiring diagram.

At this point, I would do a bench test to isolate the problem. If you can't get the two to work together on the bench, your probably wasting your time trying to get them to work in the truck.