The following custom project is tailored for a Honda Civic, but can easily be applied to other applications. For those not familiar with HomeLink, it is a radio frequency transceiver that can be programmed to operate remote garage door openers, and other radio frequency controlled toys. It is generally integrated into the visors as original equipment on many vehicles now. It is powered by the car's electrical system, so batteries are not needed, and eliminates the need for unsightly remotes clipped to you visor, or taking up space in your console, etc.
The first step was is to order the hardware. I found a set of used visors with the HomeLink system installed from a 1999 Plymouth Voyager. Here are a few things to note when buying your HomeLink transeiver. To my knowledge there are basically three different choices, besides color and style). Option A) is the older HomeLink (pre-96) which does not accommodate the newer rolling codes on a 96+ model garage door openers. Option B) is the newer HomeLink (post-96) which can be programmed for rolling codes and finally Option C) which is the newer HomeLink which also incorporates a voice recorder for making personal notes. I have seen the HomeLink transiever in black, tan and grey and in many different shades of each. Most all are the style used in this article, but VW/Audi seem to use a larger unit, or the controls are integrated into the rear view mirror. Look around and make your decision.
The next step in the process is to remove the transeiver from the visors. First gently remove the Bezel from the HomeLink transeiver. There are two fasteners just outside of the outer buttons. Reference the photo. From here this is simply a exercise in demolition. I used a razor blade to cut and remove the outer material. Next, came screwdrivers, hammers, prybars, and rotary cutting tools to remove the transeiver from the visor. I tried to salvage as much of the wiring as I could, but it really was not necessary.
Now that that transeiver is removed I would recommend temporarily wiring it to your battery and programming it to confirm its operational and will operate your intended device before cutting into your own car. Note that the white wire is positive. The transeiver does not work if the polarity is reversed, but does not seem to cause any harm if you do accidently wire the polarity reversed. Ask me how I know.
If you look over the transeiver, my original intention was to simply drill some holes in my headliner for the button pad and bezel fasteners, allowing me to sandwich the headliner between the transeiver module and the bezel. That would have been too easy. Unfortunately the headliner is too thick on the Civic to accommodate this simply installation, so I had to make some modifications to the transeiver module. Note that these modification are extremely ugly, and look even worse in the photos from all the headliner debris on it from trial fitting. I used a dremel tool fitted with a very thin metal cutting disc. I then cut away some of the transeiver housing to allow the button surface of the housing to protrude through a hole i had created in the headliner. I used the rubber button pad as a template for both the hole in my headliner and for cutting the transeiver module. This allowed me to sandwich the headliner between the transeiver module and the bezel. You can now finish off the transeiver modifications by adding about 3 ft of wire to the wiring harness for the transeiver. I recommend soldering and heat shrink for long term reliability.
Now lets tear into the headliner. I would recommend removing the visors using a Torx driver. Next use a Philips driver to remove the dome light fixture. Remove the rearview mirror, again only a Philips driver is needed. You may need a small screwdriver to pry the outer cover off the mirror mount. Next are the visor clips, located just on either side of the mirror. Now these guys had me stumped for awhile, but if you look through the front windshield from the outside, you will see a small forward facing slot in the visor clips. Use a small screwdriver to depress a lock and then rotate the clips 90 degrees and they should come right out. This should give you the access you need to insert the HomeLink transeiver.
The next step and the scariest by far is cutting into your headliner. At this point there is no turning back. As noted above I used the rubber button pad as a template for my hole size. Make sure you position the bezel where you want it and more importantly make sure the transceiver module will fit flush against the top side of the headliner in the desired position. I started by using a razor blade to cut away the headliner material, as this would avoid snagging and ripping the headliner fabric while using rotary tools to cut the hole. Next use a drill to make some starter holes and then start grinding your hole with a Dremel and small abrasive/cutting bit.
Once the hole is finished you can trial fit your HomeLink transeiver and bezel. If all fits, then you are home free. All that remains is to wire this thing up and since you have already test the transeiver, you know its going to work. The HomeLink transeiver only needs power. You can get power from the dome light. I used a fishing tape to run my wires through the headliner. Recall that the white wire on the transeiver needs positive (+) 12VDC. The other wire can be grounded anywhere on the car. When you pulled the dome light you will notice two wires. They are both Positive (+) 12VDC. The difference is when they have power. The white and orange wire is the one you want to use as it has power all the time, whereas the other only has power when the door is open. Wire to your preference. Reverse the installation of the domelight, visors, visors clips and mirror and you should be good to go.
Now you can program your HomeLink transeiver. Press and hold the outer two buttons for about 20-30 seconds to clear the memory. To program a button simply hold the desired button on the HomeLink and the button on your garage remote at the same time, making sure to have them a few inches from each other. The light on the HomeLink will blink slowly then fast once its programmed. This should only take a few seconds. If the HomeLink appears to have been learned your remote, but still does not function, then you most likely have a rolling code garage door opener. You will need to activate the 'training mode' on your garage door unit itself. You may need to reference your garage door manual for this step. My garage door unit has a red button which can be pressed to activate the training mode for about one minute. While the garage door unit is in training mode, press both the previously programmed button on your homelink and on your remote simultaneously for a couple seconds. Repeat several times, eventually it should pick up your rolling