not sure if this applies here...
reposted for discussion sake:
..The Charging System...
Most chargers on the market today are designed to charge via USB or via 12v through the firewire portion of apple dock pins (pins 19,20 12V DC and pins 29,30 Ground). This was an easy choice for the manufacturers because your car is already a 12V based system that kept the charging solutions inexpensive to make. If they already had 12V available, why step it down to 5V to charge via the USB pins? Makes sense right? As you know, Apple has eliminated 12V charging from their newer units but has left a sensing circuit on the firewire pins just to tell you that your old device doesnt work anymore. Your existing chargers will not harm the Iphone, but they are certainly useless.
The new way to charge is through the USB pins on the Apple dock connector ( pin 16 USB GND, pin 23 USB Power 5 VDC, pin 25 USB Data negative, pin 27 USB Data positive ). BUT, you cannot just apply 5V to pin 23 and ground to pin 16. The Iphone is also sensing voltage on USB Data positive (approx 1.8v) and USB Data negative (approx 2.5V).
...The Audio System...
If you had an older gen Ipod like an Ipod Video then the audio outputs were real easy, it always put line out audio through the audio pins in the dock connector. The Iphone is a different animal. The audio and serial pins are still the same on the dock connector, BUUT, there is an accessroy pin (pin 21) that senses the type of accessory that is plugged in. If the correct resistance is NOT on pin 21 then the Iphone completely ignores the connection and does not redirect the audio to the dock. Thus most of your old Ipod Interfaces are now obsolete..
I personally have an IPAC-OEM interface (pac-audio.com) to my Buick Regal that worked great with my Ipod Video (charge, audio, steering wheel controls). When I plug in my Iphone 3G, it gives me the aircraft warning (I hit no) then audio Video works fine. It wont charge, but again, audio, video and steering wheel controls work as they should. I sent them an email this morning asking when they will have an Iphone solution. They may already have it, but havent updated their site.
I also have a ic-ALPA interface from PAC that connects to my Alpine stereo in my other car via the Alpine AI-net. It will do charge and audio on my Ipod Video, on my 3G it does nothing. Ofcourse as we've seen above, it's a 12V charger which does nothing on the 3G and it lacks the proper indicator on pin 21 to tell the 3G what to do.
There's a lot of manufacturers that are going to have to play catchup for a while. Wonder how long that will take?
So, I think that settles it for the most part, I hope this helps.
TheEther...
p.s.
http://carljonard.com/2008/07/how-to-charge-your-iphone-3g-in-the-car/
p.s.s.
apple get your **** together... !