The Guide to Install GT Frameless Auto-dimming Homelink Mirror on Mazda MX-5 Miata

In this post, we are most likely to show you how to upgrade the framed auto-dimming Homelink mirror in the Mazda MX-5 Miata. The take advantage of the upgrade is both a cleaner less clunkly look and also better forward visibility by removing the frame as well as the modern shape. With the wider part of the wedge at the top, the modern mirror works much better with the headrests/hoops.

The original mirror is the Gentex/ Mito-Corp GENK40A. The factory currently uses frameless vehicle dimming mirrors as the base GENK8A, GENK80A (plus Homelink), and also GENK85A. These mirrors are sourced by several vehicle manufacturers and used on the cars, Mazda offers the GENK80A as an upgrade for the 2016-17 CX-9 with part number 0000-8C-N25. While the generic GENK80A is likewise available, the Mazda tends to be less costly.

One thing to keep in mind in this is the older mirror has an outlet constructed into the mirror itself and the auto wiring harness has a wire bundle and also plug that originate from the headliner. The new mirror has the socket at the end of an inches-long cable pigtail; the intent being that the plug connection occurs over the headliner.

 

Part and tools:

  • Gentex GENK80A mirror, I recommend Mazda part number 0000-8C-N25,
  • torx drivers,
  • automotive trim tools,
  • good wire strippers,
  • x-acto knife or similar,
  • thin rosin-core solder,
  • low-power soldering iron suitable for 24ga wires,
  • small jeweler’s screwdriver or similar,
  • good electrical tape,
  • a small torque wrench capable of 9-14 Newton-meters.

 

Let’s begin to work.

Begin by removing the pins from the plastic plug at each end of the CDROM audio cable. You’ll see a plastic tab for each pin next to the exposed metal part, pry it up slightly with your tiny jeweler’s screwdriver and the pin should slide out of the housing. Repeat for all six.

Insert each pin into the new GENK80A connector in positions 3, 4, and 5 with the tabbed part facing down/away from the top of the connector. You’ll need the jeweler’s screwdriver to push it in all the way until it clicks in place. The plug already has a red wire in position 1, black wire in position 2, and the blue wire in position 6.

Since the Mazda kit comes with a nice cable sheath, let’s use it to keep things clean. My CDROM audio cable was about 30 inches long, so I just trimmed the new wires to that length and cut off the second set pins leaving as much audio cable wire as possible. (NOTE: you might want to wait until you have the pillar and header off to check length, but that’s your call) I had trouble stuffing the three wires plus the audio cable into the full length, so I cut the sheath into shorter ~1ft sections and that worked well. If you have some braided sheathing that’d work fine as well, I sort of liked having the Mazda sticker there on the wire bundle if anyone should ever be looking there for warranty repair reasons.

Test the plug into the new mirror’s pigtail socket connector, and test all connection with a continuity tester. I used the jeweler’s screwdriver to get into the rear of the mirror’s connector and tested against the ends of the wires from the plug. If everything’s good, disconnect the mirror from the harness and you’re ready to proceed.

 

How to Install

Begin by removing the two A pillar trim pieces. From near the top pull towards the gear shift gently until it releases (two clips), then pull up from the dash slightly to free the tabs and lay down on the dash. Complete removal involved disconnecting the tweeters and is unnecessary.

Next remove the two wedges and the header trim. Each wedge has two Torx bolts and the header trim has two smaller Torx bolts. Once all are removed, pull down on the header trim to release the three tabs (center, and to each side); once free, support the trim and disconnect the plug to the light. (best to turn it off earlier so it’s cool) Set aside.

Gently pull the mirror wiring cover towards the header to disengage the clips from the mirror mount. Disconnect the plug from the mirror and use a T20 Torx bit to loosen the mirror screw until the mirror can slide upwards off the wedge. Remove the mirror and set aside.

Detach the wiring harness from the driver side A pillar and disconnect the large white connector (C17) at the base of the pillar. A trim tool or two helps pry the clips out of the pillar, do so gently & carefully so as to reuse the clips.

(Pictures below)

Unwrap the electrical tape between the two clips enough to expose about two inches of the wiring. Gently separate out the six wires identified in the table above:

Black/Red = EC- (Outside Mirror Dimmer Ground)

Black/Brown = EC+ (Outside Mirror Dimmer Power)

Brown/Black = IG1 (Ignition Switched On)

Blue/Black = Reverse signal (active when in Reverse gear)

Black = System Ground

Black/Blue = +12VDC (Constant power from battery, fused)

 

At this point I validated all of the wire colors against the pin assignments by testing continuity from the C-17 connector pin to the old mirror plug pin for each wire. It’s your choice if you do so or not, I think it is improbable that they’d have changed anything, but I’d recommend at least confirming the wire colors are correct for each pin at the C-17 connector.

It helps to tape the new harness to the old temporarily to hold it in place while you’re working. I’d also recommend laying down a protective towel to catch any solder that might drip. I found it easiest to sit in the driver seat with the door wide open and keep my tools and soldering kit on a small folding table in the doorway.

Working one wire at a time: Applying the xacto knife nearly parallel to the wire, skin the insulation. It’s mostly working by feel that you’re cutting insulation but not copper wire; skin about 1/4 to 3/8″ length, and repeat on other sides of the wire. Reversing direction helps clean it up. Ends don’t need to be fully even, but the opening needs to be free of insulation. A thumbnail helps with any extra bits.

Now that the wire is skinned, use your jewelers screwdriver or a pushpin to poke between the wire strands and make a gap. Strip about 3/8″ to 1/2″ off the correct wire from the new harness, twist the strands slightly and insert through the gap you made, wrapping back around to secure the wires together tightly. Align the new wire against the one you’re tapping into and sweat just enough solder into the braids to make a good solder joint; careful not to burn up any insulation with too hot or too powerful an iron or by applying heat too long. Again, practice on scrap wire if you’ve not done this before or just skip soldering.

Once done with the wire, cut a short bit of electrical tape (~3/4″) and wrap the joint securely.

Proceed to the next wire and repeat the process until all six wires are tapped into. Try to stagger the splices along the section of the harness so as to avoid a big bulge in one spot.

If desired, you could test things at this point. Temporarily put the new mirror on the wedge, connect it to the harness, and reconnect the C17 connector at the bottom of the A pillar. Turn on the ignition (no need to start the car) and shine a light at the mirror face with the back of it facing something dark like the inside of your garage. Or cover the sensor on the back of the mirror. You should see the mirror and side mirror darken if the green power indicator is lit at the bottom of the mirror. It should lighten when you shift the car into reverse.

If you have any problems at this point, turn off the car, remove connector C17 and start checking your connections from C17 to the new mirror connector.

When satisfied, press the wires back into a bundle and wrap up again with fresh electrical tape. Generally best to apply a little tension on the tape to ensure a good tight wrap. Done properly your work should be nearly indistinguishable from OEM.

Route the new mirror cable along the existing wiring harness, wrapping the two together with electrical tape where it makes sense.

 

Reassembly

Putting everything back together is relatively straightforward.

If you’ve not yet installed the new mirror, do so by placing on the windshield firmly and tighten the locking screw until firm. Official torque spec is 1.8 N-m, not to exceed 2.2 N-m. Route the mirror wire up and put the original wire cover in place, sliding down into the mount until it clicks. Connect the mirror wire to the new wire harness you installed and secure it in place.

Secure the old mirror wiring in place out of the way. See the locations I chose below; if you’re concerned about heat from the light bulb you may wish to consider a different location, I’d previously replaced the bulb with an LED so am not concerned.

Replace the header trim by first reconnecting the light, aligning the clips, and pressing upward until all three catch. Replace the header trim bolts and tighten, the torque spec is 4.5 to 6.4 N-m though I just went by feel.

Next place the wedges and insert the bolts, keeping them a little loose. I closed the soft top to ensure the wedges were aligned, then torqued to 12 N-m. Torque spec is 9 to 14 N-m.

Insert the pillar trim bottom tabs into place, push down slightly to seat, then press against the pillar until the two clips pop in. Repeat for the other pillar.

Align your new mirror and test it again, then program the Homelink buttons and go enjoy a cold beverage of your choice.

Closing Thoughts

That is how I did it.

I hope this post can help others who find the framed mirror pretty clunky.

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