2005 Sportster 150 gauge or sending unit?

[dga]

Hello All,
New here so pardon any greenhulk etiquette i haven't followed. As is in the title, i have a 2005 Sportster 150. The fuel gauge usually reads around 3/4 no matter what. If I give the cluster a smack, the needle moves. I have removed the fuel pump/ sending unit and played with the float and it wasn't too accurate the gauge would more or less just register full or empty, so i disassembled the gauge, dropped some oil on the little needle pinion (didn't get any on the coil) and put it all back together. With the sending unit still out of the tank i moved it back and forth again and it was working perfectly. I put it back in the the tank and it was still reading 3/4 tank. I know it is not at 3/4 because the tank is nearly empty. So out of the tank is perfect, in the tank, not so much. Any input would be appreciated. Thanks

[skidoochris]

a bad ground
a ungrounded gage will read full