Fuel Gauge Question(not Blazer related)

[NewUser]

when i got my 90 Camaro RS a couple weeks ago the fuel gauge was reading just a little past full...guy i got it from said he had just filled it up so i didnt really think much about it....did some checking and unplugged connector behind rear seat while switch was on and gauge pegged out wayyyy past full....plug it back in and gauge moves back down to barely above full...when driving the gauge seems to float back and forth moving just a little bit either way.....when i turn the switch off the gauge will move down to 3/4 tank....turn it back on and it goes back to just above full

fuel gauge and tach are only 2 gauges that dont work(tach starts out at 4k rpms upon startup and pegs after a couple seconds) do you guys think my gauge cluster is bad or do you think its the sender?

 

[dyeager535]

So you are saying the gauge essentially never moves with the changing fuel level?

Diagnosis is going to be the same as for the truck fuel gauge circuit.