Can't get key (fob) to work with my A3
 

Got my "new" 2006 A3, which came with two keys, more or less. One was a fully functional key with a working key fob (all buttons work fine). The other was a taped together bodge that didn't have transmitter board inside at all, but it works fine to start the car (so the blade is cut right, and it's got a working immobilizer chip).

I've bought two used key, one of which has exactly the same part number as the working key, and the other that was cross-referenced to the car by an online vendor. I've done the "two key programming process" about 100 times now, and have never gotten any response from the car (it's supposed to beep when you get to the point of locking the driver's door with the second key, and then press a button on the "new" remote).

I suspect that the problem might be that the car already has a full complement (four?) of keys programmed and it's no longer willing to listen for another one.

Does anyone know:
1) How to delete existing keys from the car's programming (I have a "VAG tool" that seems to have most of the functionality of the laptop tool I used when I had my VW)?
2) Any cool tricks or techniques that have worked for other poor schmoes who can't get another key(fob) to work?

Well, no one seemed to have the magic sauce, so I had to dig (deep!) to find the solution.

Get ALL the keys you're going to program to your car before proceeding

I used my VAG tool (Xtool V401 in this case), and navigated to address 46 (Central Convenience). This would be similar using a laptop with Vagcom, I believe...

Go to adaptation channel 01 (there are two "Channel 01" entries - in this case "adaptation" was the second).
- in my case, this showed 01 keys adapted (which is exactly what I was seeing).

Type in 01, 02, 03 or 04 for the number of fobs to adapt.
- I typed 02 because I had two keys, including the original
Save and confirm. The number displayed will return to 01.
- make sure and hit the Enter key (at least on my VAG tool) and you should see the screen that confirms that the adaptation was successful.
Then press a button once for at least 1 second on each fob.
- I (FINALLY!!!) got both turn signals to blink when pressing the lock button on each of the two keyfobs (the original, and the "new" - eBay - one)
Turn off the ignition and confirm the operation of all fobs.

AND IT WORKED.

I did have to disassemble the "bad key" (which still had a good blade and immobilizer chip), and use the newly programmed board and front cover (which was bad on my original, but good on the used eBay key I bought).

FWIW, make sure that the model number of any key you buy is exactly the same as the one that works with / came with your car. I came across info on the web that suggested that the "right fob" was on a different frequency (turns out that was wrong - who knew there was misinformation floating around on the web???). ;-)