I own a 07 Roomster 1.4 16 v recently the fuel gauge has started working n reverse i.e reading full when empty and the mileage display is working in unison with it i.e Full of fuel low fuel light is on and showing 30 kms left in tank and as fuel level goes down in tank light goes out and fuel level and kms left rise

 

 

Sorry I can't help, but how peculiar is that?  I hope someone with a bit more knowledge comes along soon for you!

Just did a quick google and came up with a thread that describes something similar on the Audi site.  Seems that disconnecting the battery/flat battery can do peculiar things to the petrol gauge and the answer is to disconnect a fuse and then reconnect it to reset the gauge.

 

More info on this thread, on the VWAudi forum - mods please delete if not allowed on here, not sure of protocol on this site.

http://www.vwaudiforum.co.uk/forum/showthread.php/80574-Flat-battery-now-fuel-gauge-reads-empty

I have an issue with my fuel gauge too.

It goes down too quickly when I use the loud pedal

I have an issue with my fuel gauge too.

It goes down too quickly when I use the loud pedal

 

Yes - but WHAT a loud pedal 

Yes - but WHAT a loud pedal

True enough

This is an old post but I have the same problem with my Roomster, after a flat battery the gauge works in reverse. Do not pull the fuse for the instrument cluster, it will not do anything except give you a nice new warning light from the airbag system as well as the egr light and empty fuel light when the tank is full.

The issue is most likely a faulty sender unit (worn out with age) or shorted out wire (wire shorting on chassis somewhere)