Fuel guage..Help!!

[Anonymous]

Right my fuel guage rises up off the scale every time the ignition is turned on. Sometime ago I changed the sender in the tank for a new one. This did nothing for the problem. I've now had chance to take it out again to check it. It doesn't matter what position the sender is put at the guage still reads the same. I've had the gauge out of the dash and had a fiddle around with the little setting screw thingeys on its own integral PCB but to no avail. Is there anything basic that needs checking over like shorting out wiring etc. before I go and shell hard earned cash on a new guage? Plus how does it work & why does the guage always read off the scale and not just stay at zero? I understand that the sender is like a rheostat allowing more charge(or is current)- its the guage that baffles me.
Cheers!