VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 1931 Fuel Gauge Problems

Do you know how much DC voltage should be coming out of the fuel gauge out to the fuel tank sending unit? I measure 6 volts into the fuel
gauge and 0.50 volts out and measure 0.50 volts at the wire connecting to the fuel sending unit. I installed a new sending unit in the tank after I reconditioned the tank, but didn't verify with the harness and dash gauge. I read an old Chevy tech newsletter from 1931 which commented that if you accidentally land the hot lead from the ammeter
on the gauge terminal labeled "tank" that you can damage the fuel tank sending unit. Does anyone have experience with this? This is in a 1931 Chevrolet Independence AE Coach.

Thanks

The fuel sender should read an ohm resistance to ground and should not have voltage. The gauge has voltage on one side and the grounded resistance wire from the sender on the other. With the voltage lead on the gauge and no lead from the sender, gauge should read full with power on. The gauge should then read empty or somewhere in between full with sender attached but grounded to the chassis. I always run an additional ground wire to the top of the sender from the frame so there’s no loss of ground through the tank straps and chassis mounts. Trying to remember but believe the gauge should read 0-30 or 40 ohms when cycled through the float range. Empty is zero ohms with full being the 30 or 40 ohms.
Easy to test both the gauge and sender as I described above with a ohms meter on the sender and with the sender lead removed either from the sender or the gauge. You do have to make sure power is on the correct stud on the gauge. Put one lead of the metal on the sender threaded stud and the other lead on the sender body. Cycle the float arm and the ohms should change accordingly to the motion. Just a thought here to consider: voltage present on a rheostat in a tank of gasoline would be a bad idea so that is why the sender is ground and not voltage.

Hopefully I didn’t have a brain fart anywhere and get the ohms or the gauge reactions to power wrong, I haven’t messed with the fuel gauges in a while. I do know I’m correct on the sender being ONLY ground and not powered with voltage.