Special thanks to Andivic and unclemat The JDM wiring diagrams did not contain any information about the folding mirrors, so I had to take the button apart and also do some continuity testing, as well as a little thinking.
JDM Folding Outer Mirrors Walkthrough
) Remove front door cards and the interior cover to outer mirrors (as per post#9 and #10 of http://www.legacygt.com/forums/showthread.php?t=103658
). Unscrew the three bolts holding the outer mirror (one of which is covered with a plastic cover). Remove the USDM outer mirror.
)Disassemble JDM mirrors
a.Heat the black trim around mirrors (about 2 minutes) and very carefully remove the mirrors by prying the mirrors up with a couple of small flat head screwdrivers. Mirrors are held on with black adhesive. If the JDM mirrors have the heated option, disconnect the two wires and skip to #3.
b.Unscrew central screw and remove mirror base.
c.Unscrew bolts holding mirror motor mount (not the bolts holding the motor to the mount) and signal lens.
d.Take off the scalp cap and unscrew the bolts holding the signal lens and bolts holding the mirror motor mount from the outside and disconnect the blinker harness.
e.Unscrew the 4 bolts at the hinge of the mirror
f.Pop out the plastic rectangular cover on the medial side of the mirror housing. Remove the folding motor assembly from the side mirror housing.
g.Run two wires down the harness for the heated mirrors and terminate in insulated female quick connects on the mirror side. Reassemble the outer mirror leaving the JDM mirrors off.
)Remove USDM mirror (as described above) and assemble on JDM mirror base after connecting the wires for the heated mirrors (does not matter which wire goes where).
)Put the side mirrors back on the car. I wanted to keep the car’s wiring intact, so I cut the side mirror harness #2 and #5 wires and tapped in the two wires for the heated mirrors onto the stubs left on the plug. The #2 and #5 wires to the mirror are the brown (fold) and gray (unfold). I connected these wires to some 22 gauge wires (red and green).
)Remove the plastic trim under the steering wheel (2 pop-its and plastic push piece for the lower piece and a screw in the lower right-hand side and several clips for the upper piece). Remove the plastic trim medial to the side sill (pull up hard) and then the plastic side cover below the hood release and corresponding piece on the passengers side.
)Pop off the rubber grommets of the rubber loom at the hinge of the door. Make a cut on the rubber where it enters the door past the upper grommet.
)Run the wires down the door, through the hole in the door and into the cut in the rubber, and down the loom. Run the wire into the cabin through a hard plastic inlet. A greased coat hanger is useful for this. Repeat for the other door.
)Run the wires to the driver’s side and tap the brown wires together; repeat for the gray.
)Run a +12v wire to the driver’s side. I used an add-a-circuit and used the door lock fuse (top row, third from the left), this is a constant +12V as I wanted to be able to fold and unfold the mirrors without have a key in the ignition.
)The +12v wire goes into the #4 position in the harness. Brown goes into #11, gray in #12, and run a ground into #13 of the harness. Plug the harness to the JDM button assembly.
In this picture (below) the red wire is constant+12v, the green is ground, and the two wires pointing down are tapped into the brown and gray from the mirrors.
)Reassemble all trim pieces.
Make sure you get 4 OEM wire connectors to fit into the harness.