(complete instrument panel removed)
Pull out bulb holder and plug connectors.
When installing:
green-white +
brown-yellow G
Remove the screws.
Take off the fuel gauge.

11520002 - click to zoom
 
Check fuel gauge.
Detach brown-yellow wire from fuel tank float and connect
to earth (ground).
Switch on the ignition momentarily.
The fuel gauge needle should be deflected right over to
the full position.

11520003 - click to zoom