Retrofitting notes: HomeLink for Audi A5, A4 B8 and A6 etc. (by LoCal)2.9.2008 (updated 15.10.2009) - A fellow Audi enthusiast LoCal sent in this contribution.
Based on a discussion at A5OC.com I collected these notes and ideas on retrofitting HomeLink. It is not complete or tested in any way, but something to get you started. Hopefully these notes will help someone move forward with this project and to find out more.
UPDATE 15.10.2009: Audi Original Zubehör is now offering an OEM retrofit HomeLink solution, that looks very nice and works like the factory version, although slightly different place for the buttons - judging from pictures looks factory-quality. See Audi.de and go to Audi Original Zubehör. Part number 8R0 054 602.
HomeLink is an universal transmitter that can be programmed to replace remotes for e.g. garage door openers. In the above-mentioned Audi models and probably others like them (Q5/Q7 etc.) the HomeLink buttons, when the option is installed at the factory, are located in the front roof light console (along with the sunroof controls etc.). The HomeLink radio transmitter is located behind the front bumper (A6) or behind the front grille (A4 B8/A5), see the cars manual (HomeLink section) for the exact location. (In older Audis the whole buttons and transmitter may have been inside a sunvisor, which required only power cabling and replacing the sunvisor.)
In this thread on A5OC.com (http://www.a5oc.com/forums/showthread.php/homelink-retrofit-possable-4225/index.html?p=46097) Bungle2822 researched the parts and prices required for retrofitting HomeLink to an A5 (in the UK):
New lights console dome with the HomeLink buttons £130
Wiring looms depending on what is installed in your car and what the installer finds there £40 - £100
Holder, screws etc. for the HomeLink transmitter £80
The actual HomeLink radio transmitter £430
Labour to remove A pillar trim and possibly front grill/bumper 6 hours
The notable information gathered from above is that there are likely to be two main components to a HomeLink retrofit: the button module that goes to the roof light console dome and the radio transmitter that goes behind the front bumper plus associated wiring.
The parts, minus the wiring, will probably easy to aquire from Audi parts departments, wiring may be more tricky if you need to buy unnecessarily large wiring looms inteded to replace entire wiring sets in your car instead of just adding the necessary wires. You could probably build your own cables or ask Kufatec.de, who specializes in things like this, to make you the necessary cabling.
The actual installation would require removing the roof light console and replacing it or parts of it. Instructions for removing this component can be found in your Audi manual in the sunroof section, so that is easy. The A pillar just pulls out in the latest Audi models, but some care needs to be taken due to airbags. You will probably also need to remove the glove compartment. Notes and instructions on all of these steps can be found in the Bluetooth retrofit articles on this site see the index page (http://www.geocities.com/a6retrofit/ - there are both English and Finnish language articles by the site owner), they are for the A6 but probably A4 B8/A5 are quite similar.
Also, you might probably be able to do this easier if you do not route the transmitter to the front of the car (installation there might require removing the front bumper since removing the front grille requires removing the bumper). Depending on the size of the transmitter and how well the radio signal gets through, you could try installing it behind the glove compartment or near the roof light module in the roof or near the A pillar somewhere. Power and ground can be found behind the glove compartment when it is removed, again see the Bluetooth retrofit articles (also the one on alternative/easier installation option for Bluetooth) on the index page.
Some interesting links to look at for general Audi retrofit advice and help:
Also, an easier alternative suggested by 55 JWB at A5OC.com, tiny cigarette lighter remote HSZ1/HSZ2 from STP garage doors here:
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