I upgraded to a 3G, 130 amp alt a couple of weeks ago. It is used, but tested good on two different occasions, 15.2 volts. The car has been running fine since the alt upgrade. Today I drove the car about 5 mile with the A/C on, fog lights on, and the stereo w/ 4 channel 90W x 4 mildly cranked. After being parked for about 30 minutes I tried to start the car up but got nothing, not even clicking. The car started right up with a jump. I drove the car home, about 5 miles, with only the head lights on, shut the car off and started it right back up with no problem. The battery is a few years old. It is not a top of the line battery. Is my battery going bad or is the alt not charging?