Really weird fuel gauge problem on type 44

[Eyvind Spangen]

The fuel gauge in my '86 100q doesn't work. It quit after I changed
the fuel pump.

When I turn on the ignition, the gauge just sits just below the red
part. But - the weird thing is - when I use my multimeter to measure
resistance on the terminals on the top of the fuel tank, I get the
correct resistance. I had about 1/2 full tank, it indicated 320-330
ohms. I filled up and got around 650. It looks like the thing inside
the fuel tank is working.. If I brigde the terminals on the cable
going to the gauge, it goes right to top. It looks like the gauge
itself and the wiring is OK too.. Then I tried contact cleaner, no
difference.. I even installed two wires between the gauge terminals on
the tank and the connector, nothing happened..

Anyone have any tips? I don't understand what can be wrong now..

--
E. Spangen
'86 Audi 100 2.2 CS quattro