hmm, dont know, but this may be wroth checking....
in the front of the facia, theres a little vent that draws in air from the cabin. This is used to take the cabin air temperature. linked to this vent, near the climate unit, is a fan is used to suck air into the sensor fro mthis vent.
When fitting a stereo once, I powered it on when it was outside the dash (ignition on).... as you know, after about 5 seconds the climate kicks in with the ignition switch on. As i wasn't planning to unplug the stereo again, i didn't turn the ignition off, just stuffed the wires in, and pushed the stereo in.
About halfway through putting the stereo back in the din slot, i hear what i though was a loud shorting noise, and
sh@t myselft, thinking i had pulled loose a connection somewhere.
anyway, the real point of all that, was that I discovered i had stuffed the wires back too far, and one had got caught in the fan described above. I'd imagine that if i'd kept on pushing, it would have sounded like the sound you have described.
