Is my petrol gauge haunted?

[Noddy]

The problem:
Normally when you get in your mk4 and turn on the ignition, the petrol gauge will whirr into action and register how much juice you have in the tank. Over the last couple of days mine hasn't budged a millimetre despite having £25 worth of Shell's finest sitting its it's greedy little stomach. After about 15 minutes of driving the petrol needle will begin to swing wildly from empty to half-full and back again. There doesn't seem to be any noticeable pattern to this.

Possible causes?
I've been fitting new ICE recently and also had my original clocks out for a day or two while I experimented with a modded instrument cluster I put together from scrap parts. However my battery seems fine, the ICE has been in for over a week without problems and my original clocks (which are the ones registering this fuel fault) were not dismantled or modded in any way and the mutliplug at the rear is firmly attached.

WTF?
Any idea what this could be then guys? I've searched the forums and found people with similair problems but most of the time they have done pretty obviously destructive things to their instrument cluster and/or had other problems with the dash. This ONLY seems to be affecting my petrol gauge - nothing else?!

[vdubyabush]

hi mate, i had a similar problem and also my speedo started doing it... all i found was that a fuse had gone soon as i replaced it... it was fine

[Noddy]

Ahh excellent, thanks mate, which fuse is it though? I've misplaced my Haynes somewhere between Newcastle and Leeds..

[polo boi]

my speedo workd the odd time

[polo69]

my petrol light comes on, and goes off again.

I know it cant be empty, but think its since i stuck an air filter on it.

[vdubyabush]

i`ll find out for you tomorrow