Okay, so today i was wiring up a new amp in my boot, it's an upgrade from my old one. Everything was going along smoothly, i then opened the dash and pulled out the head unit and plugged in my 2nd set of RCAs which had just been put in the car. I tested the audio, it was working fine, and then all of a sudden the head unit goes dead!

The head unit is not working at all, all wires were soldered and connected perfectly about 6 months ago and haven't caused a single problem to date. This is not my main problem though,

The MAIN PROBLEM is that the trip computer and fuel gauge are both not working at all. The fuel gauge sits on empty even though there is a half tank of fuel and the trip computer doesn't even turn on! Also the cruise control no longer turns on either.

I checked the entire fuse box, one of the audio fuses was blown so i replaced it but it didn't make a difference to anything....

:( what did i do?!

Try redoing your grounds, and check all fuses not just the audio ones.

Did you even check the fuse box in the engine bay?
Mainly the two inside the yellow box, theres also a audio fuse in the engine bay box, from memory its a 20A fuse (yellow one)

yeah make sure you check the two fueses within the yellow casing sorta thing in the engine bay...pull the yellow box up and then you can remove the fuses...will no doubt be one of those

Check the all fuses, replace what need to replace, and from my knowlege the head units have fuses to.
If they blow again it's mean some of the wires are not in the right spot. TRIPLE CHECK the wires before to reconnect the head unit!!!
The ground from my head unit i connected to the ground from cigaret lighter!
Hope been helpfull!

to reiterate my first post: I checked EVERY single fuse in the fuse box in the engine bay (including the fuses in the isolated yellow area) all are working fine.

I still can't understand what would cause the stereo, fuel gauge, trip computer and cruise control to stop working at the same time?

Mate, how did you check the fuses? visual inspection or with a multimeter? I suggest you try again as you've missed one clearly. (well from the sounds of it) Either that or you've left and earth off...

You havent done anything to the wires that run under the carpet to the fuel sender and the tail lights have you? I know that when the brake lights blow you lose the cruise and if you added wires to your amp and ran them next to the cars loom you may have accidently broken/cut a wire somehow. This could effect the fuel guage and t/c.

All of the above is just a hyperthetical and may not be the case!

did you check the fuses under the steering wheel as well?

Do your interior lights and parkers still work?
when i rewired my HU i left the Hazards disconnected and shorted the parkers fuse...
i had no indicators, HU, interior lights or brake lights...

took a while but i realised it was something small and simple. i reckon double check your earths as well...

I had a problem like this in a car once - it was a in-line fuse under the dash that needed replacing to fix things.

Good luck.

if you end up checking all fuses and they are all fine, go back and check all the wiring you where near, check for nicks in any of the cable where it could be shorting out...also check for black shit (burn marks) on the cables.