Gauge stuck past full (3 O'clock)

[Jq5x5]

I've been having this problem ever since I bought this truck, The truck is a 1983 k10 Scottsdale 6.2L diesel. When I first bought the truck the fuel gauge never worked it would just bounce around from E to 1/2, so I decided to leave it alone because I was afraid that I would screw up a wire and the truck wont start. But after running out of fuel so many times I've decided to try to fix it. I found this video that told me it was a bad resistor and so I replaced the resistor well that fixed it but now the gauge is past full (3 O'clock)
So I rewired the sending unit wire directly to the gauge since the original sending unit wire had to plug into 3 connectors to get to the gauge and those connectors were melted due to the exhaust. After I replaced the wire the gauge still don't move correctly and is still past full but it will bounce down to about a quarter of a tank and then go back up, The sending unit does have ground and is working correctly since I had just bought it and hooked a multimeter up to it and it reads correctly I'm just confused at how its not working I've tried almost everything. Do any of yall have any solutions or ideas?

 

[Ron Sebastian]

I'm in the same boat. Stopping by a local shop today to see what they can do. Tired of searching for the answer. I know it's a simple wire thing, that's disturbing.

 

[Jq5x5]

Found the issue, It was that the connector on top of the sending unit was wired backwards cant believe that was the reason for a 15 year long issue.

 

[Ron Sebastian]

Dropped the gas tank for the umpteenth time to inspect the brand new fuel pump and sending unit, all good. Disconnected each connector between the tanks and the third brand new switching valve. All good. Can only be the switching valve internal, because the right tank fuel level reads correct, the left tank pump works and engine runs great, but gauge stays on the last right tank level. This issue is really getting old.

 

[dvdswan]

Which brand of switching valve are you having troubles with, so we know to stay away from them.

 

[Ron Sebastian]

AC Delco U7001. Bought one on Rock Auto, one on eBay and two on Amazon. What the hell, all the reviews on Amazon say they are great, fixed the problem. Am I buying the wrong item?

 

[smullen]

I'm having a similar, but maybe different issue.

When I go to the pump and fill it, FULL. the gauge reads a tank and a half. LOL....

It never flakes out or moves erratically and it seems to move to reflect fuel usage.
I'm not completely sure if moves as it should, just off by at least a quarter, because I have only put 1 (maybe 2) tanks of gas in it in the month or so that I have had it.

I figure if its under 3/4 tank, when I leave the driveway, I'll go fill it up. But I'd like to have it work as it should.