Sender unit is a floating plastic knob on a bar that slides up and down in the fuel. A sensor sends a signal to the ECU telling how high / low the level is. I believe the ECU 'buffers' that signal so the gauge doesn't wobble all over the place. This buffering means that the gauge probably wouldn't "flicker" up and down if it was the sender unit.
I think +1 for the brass grounding nut on the back of the cluster. If SI batteries were the case, then the temp gauge would go fritzy too.
Next time it acts up, gently pound like a monkey on the dash over the gauge. If it responds to your pounding by flickering / correcting, then its probably the ground. Remove the cluster (5 mins, no steering wheel removal necessary) pull the back off on your kitchen table, find that brass nut, clean it and polish it with some emery paper and presto.
i haven't had a working gas gauge since i got my car last year. I go by an avg of 10km/L If i put in 20L i have an avg of around 200km. Good thing my low fuel light works.. when that goes on i have about 60km before i really need gas.
I had my mechanic take a look at the issue when i had to get my tank replaced. they even replaced the floater.. so i tlooks like the cluster needs to be cleaned.
and the batteries too? anyone know what kind of batteries they are so i can get them ahead of time?
They're ni-cad AA batteries, soldered to the board. You can get a two AA holder and solder its wires to the board to make it easier. Its best to pull it apart and see what you're comfortable with doing.
So i opened my cluster and cant seem to find the batteries......I checked the ground nut it seems to be nice and tight and the fuel sender seem to be working fine cause when i checked the sender and emptied it out my low fuel light came on. That should be a sign that it works...if i'm not mistaken.
here is some pics...if someone can point out the batteries for me