fuel gauge stuck on full

[knightal7]

Hi my fuel gauge is stuck on full and does not go down. The fuel warning light comes on when it gets low so i'm sure the sender unit works fine i have tested the tank sender unit and it seems to be ok as it reads a variable resistance as i move the float up and down.
Anybody come across this problem before and if so is there a fix for this or will i need to replace the gauge.
cheers