Schematic? One gauge terminal gets battery voltage. The other terminal gets connected to the sender. If you supply voltage to the wrong gauge terminal you could fry the gauge.
Gauge needs grounded. Sender needs grounded.
Bryan mentioned that his tank was grounded. Just to be perfectly clear, it's NOT the tank that needs grounded, it's the sender flange. One of its screws needs a special wire to the truck frame.
All persons installing new gas gauges and senders need to test it all together on the bench before installing.
I don't think some of the folks here understand how to test. Especially when a new part allegedly "does not work". We would have to see pics of the test or have the exact test procedure explained including how grounding and power was arranged. Vendor Part numbers of parts. Without details, this will be a guessing game and very hard for us to identify the problem. Ground, power, the gauge, the sender, mis wire.
