I bought a Gentex GENK40 Homelink mirror because my car didn't have one (sport package). I like the auto-dimming function too and was contemplating getting one with a compass (GENK45). Finally I decided that the extra price for the compass is not worth it, so I ordered the GENK40 from here. Alternatively, you can try using this link for a little better price; it may or may not work. Another source is this site but I wasn't too happy about the order procedure there.
Sometimes these kind of mirrors can be found on eBay for the best price (I saw an auction ending at about $150).

You also need a wire cover (the longer one) to make the installation look neater. Otherwise the bare wire would be visible above the mirror.

Here are some pics, showing the stock mirror (bottom) and the Gentex one (top). As you can see, the stock mirror's mounting bracket (and the mirror button on the glass) is a little narrower, so we have to deal with this little discrepancy later.

 

To remove the stock mirror, use a small flat-blade screwdriver. On the bottom of the mirror bracket, you see a notch - this is the place where you shove in the screwdriver and push it towards the top, pretty much vertically. The goal is to reach and unlock a metal spring-like plate that holds the mirror to the window button. See the red arrow on the first photo, showing the backside of the stock mirror mount. The arrow points to the metal strip that needs to be pushed up, and at the same time, you should grab the mirror and push upwards, trying to slide it off the mirror button (thanks Aseras for the help).
This was kind of a pain because first my mirror wouldn't budge at all, but perseverance paid off

On the left the stock mount, next to it the backside of the Gentex mount:

 

Now we have to fix the issue of the mirror button on the glass being a bit too narrow for the new mirror. The Gentex mount slides over the button fine, but it can't be tightened properly and the mirror would move side-to-side and even back and forth a bit. To eliminate this, I used a strip from a plastic clamshell packaging everyone loves to hate - I'm sure everybody has some of these laying around.
Just cut a strip wide enough to cover the area between the top of the mount and the tightening screw. Then, fold it up to fit into that space like the photo shows. I heard that you can use the same material and fold this piece so that the tightening screw will be driven into the 'pad' you're building.
The following two pics show the strip I used, and the folded pad. Yeah, ghetto but it works very well. Never mind the toothpicks on both sides - I thought I'll need those to avoid movement side-to-side, but it turned out not to be the case, so you don't need anything there.

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Instead of using the plastic packaging to fabricate a shim, you can use a small nut or something similar, so that the screw will bump into it. This adds the necessary thickness to the mirror button that the new mirror needs. This is a better solution than the plastic, since that can become loose over time. A proper metal shim under the screw will not.
I replaced the plastic with this method in my installation.

 

The next step is to slide the new mirror's mount over the button on the glass (going from the top). Take care not to dislocate the plastic pad. It's easy really. Then, tighten the screw so that the mirror sits firmly and securely. You'll need the proper bit for this - it's a #20 Torx.
Once the mirror is on, you can start leading the power wire to it. The wire will be tucked under the headliner, then moving to the left towards the driver's side A pillar. The wires are not too pretty, so now you'll use the wire cover that will look much better between the mirror and the headliner.

 

Take off the plastic A-pillar cover. You should pull a bit upwards first to disengage the white plastic fastener from the cover (marked with the circle), then pop out the two lower fasteners. Lead the wires down from the headliner along the A-pillar, then behind the weatherstripping and plastic panels at the door. I used some tape behind the A-pillar cover because there isn't any good way to zip-tie the wires to anything there. Hope it'll hold

 

I decided to connect the wires at the fuse box down at the driver's left foot. We need a ground point, a continuous 12V and a switched 12V source.
Lead the wires to the fuse box from behind the plastic panels, so that no wires are visible. On the picture of the fuse block, I marked the eyelet (or whatever it is called) that will attach to the ground spot with the arrow. I found a convenient bolt, but for this, the eyelet's hole had to be enlarged a little - no problem, a round file or a proper size drill bit will take care of that. The bolt for the ground is shown on the next two pictures - it's right above the fuse box, on the inside. There are several other possibilities for grounding in this area, but this one was convenient enough because I had a matching nut at hand, and access is pretty good, without having to remove any additional plastic pieces.

 

After attaching the ground wire, two convenient locations for the power sources are the fuses located at the top and bottom. The first one is for the cig lighter which is switched, the bottom one is the ROOM fuse which is constantly powered. I just cut off the splicing connectors these wires came with, stripped the wires a bit and wrapped them around one leg of the fuse, then pushed them back in place. Yeah, ghetto again but they sit very securely and don't look too bad. Perhaps I'll get one of those fuse adapters at Autozone or someplace that allow making such connections in a neater way...
One thing to mention is that the mirror's installation instruction wasn't correct when describing the wire colors. It said the black wire with the white stripe goes to the constant 12V source, and the black wire with red stripe to the switched 12V. Problem is, mine doesn't have a red striped wire. One is solid black, another one is with a white stripe. The one with the white stripe has to go to the switched source (as the photo shows), and the solid black to the constant 12V. This is important otherwise the mirror's auto-dimming feature is always on and you risk draining the battery.

The last pic shows the final result - now all what remains is to program the buttons according to the instructions, and you're set. Enjoy your new mirror

 

Nice DIY, I think I will put this on my Christmas wish-list

Why didn't you use the "free button kit" they mention on the website?

 

Because I didn't feel like taking the stock button off the windshield and risk damaging the glass.
This seemed to be simpler

 

The stock button is not going to come off. the rx8 i got my homelink mirror from had the glass come off with the button.

tamas stole all my ideas too

good job on the DIY. I never got around to doing one.

 

Thanks for the writeup. Installed mine yesterday and followed your method. The plastic shim method works as advertised. The mounting seems quite secure. And since I no longer have to keep torquing the "day/night" lever, it should stay that way.

One thing to note when placing the shim material -- take care not to block either of the 2 notches at the top of the mount -- the wire cover has 2 prongs that snap into those slots. If your wire cover doesn't want to snap in, you may need to loosen the mount and shove the plastic down a tad.

I didn't have a nut to fit on the bolt Tamas used for ground. Which is unfortunate. As he notes, that's really the most convenient ground point in the vicinity. The other reasonable spots were obstructed. I opted for a bolt that is located above and just to the left of the fuse block, against the side panel. Had to remove the side rail plastic and then move the piece surrounding the fuse block to get access. The wire color-coding was as Tamas described. The manufacturer instuctions were similarly wrong for my unit.

I must say, this mirror is even better than I thought it would be! I'd basically wanted it because I was tired of the mirror always becoming misadjusted when flipping from "day" to "night". The homelink thing being a nice bonus. Now that I've used it, I realize just how nice it is to have the dimming constantly adjust to just the right amount instead of just "on" or "off". Really maximizes rearward vision, imo. The amount of dimming seems just about right to me, from barely on with cars in the distance, to a very dark tint when someone is right on your tail.

The instructions that came with the unit could have used more precise language -- it took me a while to get the homelink programmed. Programming actions can result in "slow" or "fast" blinking of the indicator. Which isn't very useful description until you've seen both modes. Compounding the confusion was the fact that the initial "erase" action is supposed to result in the "fast" blinking, though it turned out to be the "slow" mode in my experience. For reference, "slow" blinking is about 2 times per second. "fast" blinking is more like 6 times per second.

 

Guys, do you have the diagram for the connector on the mirror? My wire colors are different: black, black w/green stripe, black w/red stripe, and black w/yellow stripe.

Edit: Nevermind, I got it wired up.

 

Awesome write-up. Very helpful.

One thing I could add is that if you find yourself with a homelink mirror to add (salvage, eBay, etc) but not the wiring harness, Mazda part number 0000-8C-H16 did the trick for me.

That's the kit for the 6, but the connector to the mirror is the same and the instructions in the kit line up very well with the instructions above.

 

i actually got the mirror and wire off a rx8 that had one and i was wondering how the wiring worked for that coz the harness he cut off for me has one blackgreen one blackred one blackyellow and a black which im guessing is the ground so i was wondering if anyone knew how to wire this up ...

 

There is someone wanting to trade straight up for a non home-link mirror in the FS forum.

 

yeah thats who i got it from but i was wondering if anyone could help me with the wiring coz my colors are nothing like the ones on this diy

 

thought i would share what I did... also considering making a thread for this

 

just a small update; the roof harness from rx8's that have homelink is plug and play into your OEM dash harness so by purchasing the homelink mirror and the roof harness you can install a homelink mirror into your car with no soldering or electrical work required. Just run the line through the passenger side A-Pillar down to the foot well where you will find the plug next to the alarm sensor and run the harness into your roof where you will plug in for your visors, map light, and your newly installed homelink!