I was driving for a few hours yesterday with my headunit on loud too.

Then suddenly, it all stopped, the headunit just turned off - no noise, no screen display, nothing.

The headunit's had to been repaired before so I thought that it had blown somehow.

But this morning I tried another aftermarket headunit - again, it didn't work, so I thought it must be the wires

Then I tried the stock headunit and much to my surprise it worked fully! Screen, sound etc.

To double check the other units I tried them in a different car and they worked perfectly.

Does anybody have any idea what this could be? Left me stumped.

You have blown one of the 2 supply fuses. The oem headunit doesnt mind working on one supply, aftermarket units tend to need both.

Blew a fuse? PHEW. I'll go try changing one, cheers.

I had a look in the fusebox and I couldn't see any blown ones... do you know which fuse number it's supposed to be? or is it located somewhere else?

Using this diagram I checked 42, didn't seem blown, replaced it just to be safe, and still the headunit didn't work. I also checked & replaced for safe measure the fuse on the headunit. I also checked fuse 37 and it wasn't blown.

-- Actually, looking at that diagram, it says it should be a 25A fuse (for #42) even though the one in there was a 15... and wasn't blown. Do you think that would effect anything? Doesn't seem like it should.

To find out if it is the supply, measure the output voltage of the switched and permanent live at the connector end. (Red and yellow wires normally)

Or if you don't have a multi meter just connect a wire straight from the positive of the battery and connect it to the red and yellow inputs to the aftermarket stereo.

Use a fuse in line as close to the battery if you can, especially if you suspect the head unit may be faulty.

Cheers for the help peeps... Couldn't figure it out myself in the end so got a professional to rewire it.