My 05 Lariat has electrical issues to the mirrors. They are heated, power, turn signals, without power fold. Everything in the door works fine except the power adjust. Or at least they're supposed to have power but not. I lost the power last fall but trucks been in cold storage for the winter here in SE MN. I've been having intermittent battery draw problems as well for about the same time so they are likely related. I did all the typical fuse checking all possibly related fuses with my Fluke and visually as well. I went by the owners manual and tested everything with the fuses being the exception in the drivers door using a known good COMMON ground. The fuses listed were numbers 3, 4, 8, 18, and 114. When removing the switch the ring cracked so bought a new switch. No power to the switch though. Where might be the best place to go from here? I've looked at some schematics but some have had different shaped plugs and differences in wire color so kind of at a loss as to what is correct and not!!! I'd be ever so grateful if someone might be able to offer some expertise on this for me. My truck hasn't seen a snowflake and has under 114,000 miles on it. Looks and drives like new but now the mirror issue from hell arises. LOL Thanks!!

Frankenford

 

I have the '05 F-150 Lariat as well. I have a very similar issue. Only, it affected the drivers seat, as well as the mirrors. Turns out, in Ford's infinite wisdom. they put a "splice" in the wires not to far from the fuse box and close the to bottom front side (inside) the passenger door kick panel. That "splice" corrodes, and eventually fails.
Remove the kick panel, and the door step cover to work on this. have a solder iron, solder, and some good heat shrink and maybe some silicon available. You should be able to fix this in an hour or so. I apologize, but I cannot remember the color of the wire, I think it was an orange wire with a black (or maybe brown) stripe on it. And am sure there are others in here that can give you more specifics. And now that I think about it, I may have found the solution in this forum. :-) Cheers!