Scirocco Register

As of a couple of weeks ago my no.3 fuse blows as soon as I try to replace it, so I have no stereo/central locking/interior lights etc.
There has been water in the passenger footwell due to a leak but the fusebox and surrounding wiring is all dry, as is the stereo wiring behind the central console. I replaced the fusebox after a leak a couple of years ago and feel confident this time that water in the fusebox isn't the problem.
It looks as though water was getting in somewhere near the central console, but I think that resealing the blower and the windscreen has stopped the leak now.
However the electrical problem remains. I can't see any sign of it being due to water this time.
Please does anyone have any advice on how I can track down the source of the electrical fault?

Sorry I couldn't resist and I can't really help. I would just get a multimeter out and get testing the wiring from the fuse box plug to the parts that relate to fuse 3.

start with unplugging as much as you can from the circuit. take bulbs out of all lights on that circuit and unplug the stereo. put fuse in and if it doesn't blow, replace stuff until it does.

favourites will be a stereo that has developed an internal fault or been wired in by a muppet, or a light bulb that has blown and is now shorting out