I suggest you have a thorough look under the dash, passenger side (behind glovebox). A mirror and a good flashlight might be enough to see from both sides of this connector.
On mine I can find Mirror Defrost +12V LG (Light Green) wire coming from the firewall, but it stops there. Nothing is connected on the other side on C04. Door harness is complete though.
That a project I'll finish later this summer... but from my understanding, I'll need to tap from this wire to feed both doors harnesses.
Which wire where? So the wire itself is present coming into the cabin? Or there's power that comes into the cabin but there's no wire in the cabin? Is it a switched 12v or switched ground? If it's switched 12v and we know where the appropriate wire is I don't have an issue running my own wire and just grounding in the door. If it's a switched ground, same difference because I can just tap the 12v constant going to the puddle lamps I installed in the mirror housings (or which will be going there once I wire them up inside the car. ).
If none of that works could we use one of the wires coming out of the back of the HVAC controls to trigger a relay to power the mirrors? If so do you know which one could be used as a trigger?