I have swapped the power mirrors in my 04 FX4 for heated signal mirrors. Power and signals worked out of the box, however I do not have the button for the heat. The wires are in the mirror harness in the door however.

So I had 2 options I was exploring, wondering what one you all think is better.

Option 1, was install a toggle switch and pull power from somewhere and just splice into the heat wire going into the mirror.

Option 2, was something I saw someone else mention about just putting a switch on the wire for the factory switch. I have attached the wiring diagram, but wasn't exactly clear on how that was accomplished.

Anyone have any suggestions?

 

On my 06 xlt my mirrors heat with the rear window defroster. Not sure why you would have a wire and no switch. Good luck.