Picked up a 08 H3 a bit over a week ago. I noticed the factory head unit sometimes "lost" the drivers side channel, both front and rear door speakers didn't work, and the "chime" was at a low volume. I replaced the head unit, and the left channel was working. Well...sometimes it did. I was thinking short somewhere.
Where it becomes wierd, it only seems to work after around noon. In the morning no left channel. Break for lunch, it comes back to live, and the chimes are normal as well.
When I replaced the heat unit I used the "proper" harness that allows the OnStar to work. I don't ever plan on using the OnStar, but it should work if I ever wanted to use it.