Fluctuating Fuel Gauge

[dbc28092]

I just replaced the fuel tank and sending unit on my 1984 Chevy C30. Before installing the new sending unit, the fuel gauge did not work at all. Now, it is registering but moving all over the place. At times, the gauge shows about the right amount. Then it will start moving around and settle on something completely inaccurate. I checked the ground on the sending unit and it seems OK. The only thing I've thought about that I haven't done is run a new wire from the gauge to the sending unit.

Before I go through running a wire, could it be that the gauge is just broken?

[Irish_Alley]

could be a bad connection on the cluster pig tail

[Butalla]

I have the same problem with mine.  It's been this way both before and after replacing my sending unit.  I doubt this is a wiring issue as a wiring issue would give you a high resistance and thus a bad reading, but I don't see how that creates a bouncing reading.  I agree that the gauge is the likely problem.  If you don't have an extra gauge, you could try using one of the other gauges like the temp gauge.  Run a couple jumper wires and see if the bouncing continues.  Of course this assumes that the gauge isn't maxed out.  In not sure if this will work, but it can't hurt to try.

[Irish_Alley]

FUNCTIONAL TESTS OF FACTORY GM ELECTRIC GAUGES

[NCali]

I hate to admit that I did this but I changed a fuel pump on my truck , when I disconnected the electrical connection the plug broke apart . I inadvertently connected 12v+ to the sending unit  when I reconnected the wires and now the gauge pegs all the way past full when I fill it and it will stay there until the fuel level is almost out and then the needle will bounce when coming to a stop, and accelerating 

[Captkaos]

You basically fried the sending unit if you did that.

[Dan75k20]

My fuel gauge reads past full all the time. I turn the key on it will go to empty if i do not start the truck. When i start the truck it will go back to past full

[NCali]

Captkaos:  yea it fried the sending unit at the level of the fuel that was in the tank at the time, so when the fuel level gets to that point the needle starts bouncing and it is time to get gas, but the right tank still works fine