@Chris King posted:The push button has 2 earth wires to it, then a red wire which is joined to a light blue using an original connector clock. This runs near to the AC unit wiring, through the loom and comes out by the fuse box. Wire is integral to the loom, not been added later on. It has an original connector block on this end, and no wire out of it, so I'm unsure of its purpose.
...didn't see a comment about the light blue wire so thought I'd offer an opinion at least. With the red wire removed at the switch end, all the large blue wires in the first photo look 100% 'stock' - - the image highlights the 'doubled' AC power block, and the 'single' connector normally used to power a dealer-installed radio, when fitted. At least on earlier cars the OTHER end of that light blue wire went directly to fuse 9. So if that fuse 9 connection was cut and a load was added between it and the fuse supply, 12V would go to the load whenever the orange switch was closed (i.e., grounded).
If somebody was adding rear window resistance heat to a Mangusta, that would be one EASY way to do it. Unfortunately I have no idea if that was the factory's approach - - need input from the owner of another car with similar origins/manufacture to confirm whether or not the light blue lead is cut & re-connectorized near fuse 9. But it's definitely a possibility!