There are two problems with siamesing another supply like those you mention, the first is that the wiring and protection is designed for the standard load and increasing it with the camera means there's the risk of damage.Daewar wrote:I have one question though, did you look into using the wiring that goes to the rain sensor / internal lighting as its so close to the mirror area and piggyback on that?
Secondly, whilst we think if dashcams being 12v devices, they're actually 5v the same as all USB devices, that means you'd still have to use the hardwire kit step down transformer (or go the extra aux socket route using the cameras original aux plug plugged into it) either option means you'd have to secrete a largish box/tube adjacent to the camera.
The fuse box method is safest and neatest in my view.