RichJam

Skoda fabia 2003. My fuel gauge has started behaving erratically. Sometimes it says the tank is empty when it is actually nearly full (and vice versa). Other times it appears accurate for while but then moves up/down while driving. On the occasions when the needle reads empty the fuel warning light doesn't come on (I'm guessing the needle and light run off different systems/sensors?) I've done a bit of googling and I think I may need to test the sender unit with a multimeter to determine if this is where the fault lies. Can anyone tell me exactly where I should be placing the multimeter probes on the unit? And what resistance levels should I expect to see when the sender arm is in the full/empty position? Is there any other basic things I should look at/check (wiring?) to help diagnose the problem? Thanks, Rich