[ciamaichelo]

Over the past two months, I have experienced several dead batteries in my 2005 911 Carrera S (3.8L 997 manual). My battery is less than a year old and it passed two separate test at Kraigen and Autozone. After charging the battery, it will discharge after 4-5 days of driving to about 60%. At that time, the car will struggle to start and eventually fail to start. The battery test OK with a voltage of 12.6. With the car running and high beams, fan and radio on, the battery pulls insufficient voltage to charge or pass the alternator test, using a $15 alternator testing tool, my battery charger or the alternator test at Autozone.

I changed the alternator with a new OEM Bosch alternator and charged the battery to 100%. Thinking I solved the problem, I drove for a week and again the car was slow to start and next time failed to start, requiring a boost.

I then installed a new battery, thinking the bad alternator and frequent discharging killed my old battery. I then tested the new alternator and battery at home and at Autozone. Again, with the car running the battery still pulls insufficient voltage to charge the battery and the alternator tools also state low voltage output. I assume the voltage regulator is part of the new alternator and I disconnected and charged the battery prior to installing the new alternator.

What other components could cause insufficient charging voltage from the alternator to the battery? I read on 6Speed that a bad alternator cable could be the cause. Is there a fuse somewhere? or burn out cable? Any ideas or help would be greatly appreciated.

Thanks,
Chris