For some reason the stereo won't turn on whilst in the car,

I've tested from the original stereo loom right through to the JVC - Ford extension plug in the back of the head unit & has power through both yellow and red wires, but doesn't turn or set electric aerial off.

The red feed has a secondary feed coming off it and that doesn't have power this was the power source for my gauges

I've tested the head unit off the battery and it works fine