Fuel gauge wont stay still!!!!!

[Bartenfeld]

with all of the lights off and no turn signals blinking, my fuel gauge is fairly accurate. However, when I turn the head lighs on the gauge will drop almost half the span of the gauge.

I.E.- if is says the tank is full with the lighs off, when I turn the lighs on it will drop to half the half full mark.

Also, if I introduce the electrical current of the turn signal, it will then fall even more and jump back to the half-full mark corrisponding to the blinking of the turn signal. What is going on here???

[HOTFUN]

Bad ground on the gauge cluster. It's drawing some of the resistance of the fuel tank sender to ground back through causing causing it to fluctuate. Check for corrosion on your pin connectors and or throw an extra ground wire to the cluster case back to the firewall. Assuming you have a body ground off the cab to the frame and one off the negative battery post to the body too.

Also check that someone has not tapped a wire (looking for power or a ground) to that gas tank sending unit wire from the gauge to the sending unit in the tank.

[Bartenfeld]

thanks man! i had an idea about an insufficent ground problem, but did not completly understand the science behind it all. You've really helped me out!!