I've bought a Sony M8800 and had a bit of a 'botch' with the installation of
the head unit....

Having pulled out the factory head unit, I plugged in the ISO harness
(included with the Sony) and then connected the harness to the Sony (= easy)

It worked fine for a couple of minutes (I hadn't secured it in the DIN slot
at this point, just resting on my lap).... While testing a CD, I must have
tugged on the harness a little too much and I saw a spark inside the DIN
slot - I'm not sure where it came from, but the new head unit went
night-night.

Since then, I tried the original Golf head unit, it powers up fine. It's
asking for the 'SAFE' code. I'll have to contact VW for it, but this is not
a problem.

I've connected the new Sony head unit in my other car (Audi A4). It already
has a Sony head unit, so swapping the units was easy. The new Sony works
fine in the other car - so it doesn't seem to be damaged (tested the new ISO
harness as well, it checks out fine).

This narrows down the fault to the wiring loom in the Golf (unless someone
tells me otherwise?).

I retried the new Sony head unit in the Golf and nothing had changed (why
would it have?...). I then swapped over the red/yellow connections to change
from switched to continuous power supply. The lights still don't come on,
but I can now open and close the motorised face panel.

This means that its getting power, but something is still wrong....

Is it shorting somewhere or maybe fuse(s)?