68 GMC Sierra fuel gage/electric

[Captain J]

The problem is that no indication at the fuel gage, the fuse beside where the Tan wire (coming from sending unit) is not workin. My knowledge this wire your taking about (on top of sending unit) should be the 12v, sending unit is grounded by the tank.
Temp gauge is moving slightly when engine is idling

[Sheepdip]

Originally Posted by Captain J

The problem is that no indication at the fuel gage, the fuse beside where the Tan wire (coming from sending unit) is not workin. My knowledge this wire your taking about (on top of sending unit) should be the 12v, sending unit is grounded by the tank.
Temp gauge is moving slightly when engine is idling

Nope it's a ground wire, the tank to the body just completes the grounding circuit. The negative feed from your battery to the sending unit in this illustration is completed by your metal tank to the cab/body, the wire from sender to gauge is a continuation of that grounding to complete the grounding circuit.

https://auto.howstuffworks.com/fuel-gauge1.htm