Hey guys so my 04 gp started showing charging system failure last night so I started checking it out today and my voltage with the car off is 12.13 and when I turn it on, it drops to 11.73. Obviously that's why it's showing the message but my question is why? I am running one 12 but nothing big. I even turned off the stereo while the car was on to see if maybe it was the amp making it drop up and down but it didn't make a difference. My battery is however about 2-3 or 4 years old. It's a red top optima battery. Is it time for a new battery? Maybe alternator?