2006 Renault Master - Fuel Gauge issue

Hi,

I have a 2006 Renault Master DCi 100. It seems there is a problem with the fuel gauge. In these vans the gauge is electronic and shown on the dashboard computer by means of a stack of blocks. When the stack of blocks disappears the fuel light illuminates to indicate that you've went into the reserve.

So, I went into the reserve a few days ago and put €12 into the tank to get me through. Since I only have the van a few days, I reset my trip counter to see how long it would take to reach the reserve again. 80 kilometres later, the light came on. The next day, I started the van up (trip counter showing 95km now) and two stacks appeared on the dashboard to indicate that there was in fact more diesel in the tank. So I drove around fine until the reserve light came on again at the 125km mark. I pulled into the shops on the way home, turned off the ignition and when I turned it back on the same thing happened. Another one stack appeared on the dashboard and the reserve light went off.

I've done 130km nearly since putting €12 into the tank but am unsure of what actually remains in it. I'm pretty sure the computer must be giving a faulty reading.

I did some quick research on the internet but couldn't find anything that deals with this problem specifically. Has anyone an idea of how to rectify this?

PS: I'm not a mechanic so wouldn't be too familiar with how to get down and dirty but if it's a simple job then I should be able to manage. Thanks.