Autometer fuel guage not working

There shouldn't be any voltage through the sender wire (you're probably seeing feedback in the circuit). That wire, when connected to the sender in the tank, measures resistance relative to ground (the approx 9-72 ohms).

If you have 12v connected to the proper terminal, and the ground terminal properly grounded, when you connect a jumper from the "S" terminal to a ground, the gauge should immediately peg on "full". If you get no movement then contact Autometer - they'll send a replacement.

One I installed wasn't calibrated correctly. It read 1/4 full when there was no fuel in the tank. I sent it back and they sent me a replacement that worked correctly.