74 C30 gas gauge way past full ***UPDATE***

[chevy66c10]

I'm sure this has been brought up before but i am stumped, truck is a 74 Chevy C30, 350 4spd, passenger side 20 gallon tank. The needle sticks way up past full all the time. From what ive read thats not usually the sending unit, but a ground or something along those lines. so i ran a new hot wire from tank to the plug in the gauge cluster. the ground might not be right, but the guy had it wrapped tightly aroung a metal tab on the locking ring, and then to the frame, i did the same thing with new wire. Still went up past full. Pulled out gauge cluster, circuit board is dusty, but the only place its burned is the circuit for the blue light for high beams. Replaced the gauge then too. Now i read that some old vehicles have a voltage regulator for the fuel gauge and temp gauge, do these trucks have one? And also How should it be grounded correctly, and should i try grounding the gauge itself? Thanks bugging the crap out of me haha

[Irish_Alley]

You can check the wires in the cluster panel and see if they need to be cleaned.
http://forum.73-87chevytrucks.com/smforum/index.php?topic=16071.0
This might also help

[chevy66c10]

OK so here's what I did still with no luck, replaced. Sending unit, cleaned spot on frame for ground, ran other wire directly from sending unit up to plug for cluster. Replaced ground from cab to frame with 10 gauge wire, cleaned metal first, same thing. Gauge goes all the way over to 3 o'clock way past full. Replaced gauge with gauge out of 85 truck same thing. And if I unplug the wire from sending unit to gauge it still reads past full. One thing I noticed is the 'negative' side of the cluster circuit runs to fuel gauge and instrument panel lights and those lights are always dim.  Its wire number two on the plug for negative side grey in color, is that a ground? If so where does it ground out at and could that be causing my gauge problem. Cause is think that the gauge would need a good ground and have yet to find it please help driving me nuts!

[chevy66c10]

nobody?

[velojym]

Didja try waving a chicken bone over it?

[Grim 82]

If so where does it ground out at and could that be causing my gauge problem. Cause is think that the gauge would need a good ground and have yet to find it please help driving me nuts!

Hook up a temporary ground to test your theory.

[BigTater]

Mine does the exact same thing. When I'm using the passenger side tank it goes way past full but the drivers side works fine.  I'm curious to find out how this works out. I won't work on mine till after winter since I just run my right tank empty and switch to my left tank I don't really NEED to fix right now