Fuel gauge help

[fungusguy]

I just purchased this vehicle last week with a broken fuel gauge. The previous owner said that he had replaced both the gauge itself and the sending unit. He said that he determined there must be a broken wire somewhere but couldn’t diagnose where.
I cleaned the ground connections behind the gauge panel and on the left engine head. All of the other gauges read properly. Disconnecting this wire I have indicated in blue does nothing. Swapping the positive wire and the negative with other gauges that are known to work also does nothing/no change.

 

[TOBASH]

I had this problem on my truck and I literally had to swap the positive wire for the negative wire and the negative wire for the positive wire and voilà my gauge worked

 

[Mogman]

The sending unit needs two things, a complete path (wire) to the gauge and the sending unit must have a good ground, the tank is plastic.

 

[fungusguy]

I had this problem on my truck and I literally had to swap the positive wire for the negative wire and the negative wire for the positive wire and voilà my gauge worked

How did you do that exactly? The gauges I have are grounded through their bezel/foundation clip on the rear and if I swap them I think it would send positive to the ground of the other gauges.

 

[Jinx]

How did you do that exactly? The gauges I have are grounded through their bezel/foundation clip on the rear and if I swap them I think it would send positive to the ground of the other gauges.

He didn't swap the ground wire. In your diagram, he swapped the red wire with the blue wire.