Have a look at this website it explains the wiring and covers an always full tank problem;

http://www.austin7.org/Technical%20Articles/Fuel%20Gauge%20Working/

"If the pointer is always at 'Full' - even when the tank is empty

Disconnect the wire to the 'T' terminal, if the gauge stays at ''Full'' then there is a fault in the gauge, if the pointer drops back to `Empty' then the gauge is OK and there is a fault between the gauge and the tank."

Last edited by Clock; 20/06/16 07:41 PM.