The car wont trun over or try to start, but battary is good, got 12volts c ok me through, I'm thinking it's the starter but it could be the alternator too but I have no way to see. Anyone else have this problem?
Can you get access to a spare battery or get someone to give you a jump.
If you can get it stared you can start the process of elimination.
Had this problem with my V6 last month and after trouble shooting it was the battery.
Jumped my G8 and it fired right up so not the starter, had a multi-meter and confirmed my alternator was putting out 14V.
I don't know if 12V would be producing enough juice to make a difference or not.
All I got, good luck.