Fuel gauge ‘70 C10

[broberson]

Fuel gauge doesnt read properly. The tan wire runs from the fuse panel to the fuel sender. I just replaced the sending unit, so problem shouldn’t be on that end. The gauge, with the wire attached and with the key off reads higher than the full level. Key on, the gauge wire attached to the sending unit, the needle doesn’t move. With key on and unplug the wire from the sending unit, the needle continues to bury past the full mark, past the hash marks completely, down where the light for temp is. Any ideas?
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[Dead Parrot]

A fuel gauge powered off will often move to a random spot.

Powered on and disconnected from the sender, normal result is a way past full reading. Seems to indicate your sender wire connection is good from gauge to sender and the tank ground is good.

Powered on and no reading when sender connected might be a bad/loose/corroded ground at the gauge/cluster.

[broberson]

ok, I'll check that out. I put in a new harness, complete redo. so there is a possibility the ground I have is a poor connection.

[Wrenchbender Ret]

How about with key on & ground the wire at the sending unit? The gauge should read empty.

[Andy4639]

Have you painted the cab are anything in it? Make sure the ground is good to the body to chassis and to the battery. Check your electrical connection in the cluster. It may need cleaning good. Also make sure the cluster ground wires are in place. There should be 2 grounds for the cluster. One is in the wire bundle the other is a separate loose ground wire that attaches to the metal backing tin to the dash with a clip on it.

The second picture is what I found on my daughter 68, I couldn't figure out why nothing worked.
Last picture was after I cleaned it up.