could you post some more info(what $100 adapter)? otherwise, you might want to bring it to a car audio shop to have them install it. remember, this is a internet forum, and most of us have no clue what is causing the problem, any steps you have done, what adapters are available for your car, or if you have the correct adapter harness for your car.
This forum is dedicated to CarPCs and installing them in your car.
The car audio forum is dedicated to integrating your car audio system with your CarPC.
For specific questions related to car audio equipment systems that do not include CarPCs, I would recomend checking out car audio specific forums:
There is a chance that someone on here might have an answer for you, I would just hate for you to wait around for it when I know you could get an answer much quicker on a dedicated forum.