To take grzzlycanuck
's solution, which I think is k.i.s.s. I'll provide how to make this happen.
Things you will need to perform this FIX.
1) Soldering Gun & Solder (and the skills to use it)
2) Electrical Tape
3) Heat-Shrink Tubing
4) 3 Female Tongue Connectors
5) 1 Illuminated 12vdc switch (I used a Radioshack 275-0018)
6) 1 18" Black automotive hookup wire (I used 18 gauge)
7) 2 18" color-of-your-choice automotive hookup wires (same guage)
8) approx. 1/2" drillbit
First release the S.A.M. (the one with the fuses) from its holder (do NOT remove any wires!) so it looks like this as viewed from the left.........
Where I have label SWITCHED POWER are locations R1-R4.
The WHITE fuse holders are what we are interested in.
One of them has TWO BLACK wires with BLUE STRIPES.
This is the one we will be concentrating on. These are the heated mirrors and there is one wire for the left an one for the right.
Proceed to remove the fuse from only this fuse-holder and begin to pull the TOP of the WHITE fuse holder away from the S.A.M. like this.....
When released it will look like this.......
Now CUT the wires approx. 3-4" from the end like this.......
Now solder and heat-shrink one of your selected-colored-wires to the pair that runs off to the heated mirrors like the following......
Now take the OTHER-colored-wire and do the same for the pair coming FROM the fuse-holder like this......(also insulate when done)......
Now go ahead and connect the BLACK wire to a suitable ground and terminate EACH wire with the Female Connectors like this.......
I STRONGLY suggest you label at least one of the colored-wires i.e. the wire coming from the fuse holder as POWER.
The illluminated 12vdc switch I chose from Radioshack looks like this.....
On the back it has 3 male terminals labeled, POWER, LOAD and, no kidding, EARTH.
SEE PART 2 of 2