battery drain 1999 996

[rjf123]

The battery in my 996 keeps going dead. I replaced it with a new battery, but still it will die if the car is left standing overnight. It occurs whether the alarm is armed or not. The alternator seems to be working, as it will recharge the battery, and, when running, the volt meter usually reads between 13 and 14 volts. When the battery is fully charged, and the engine off, the volt meter will usually read a litttle over 12 volts. But, when left standing for variable lengths of time, the voltage will slowly drop. It seems that if I disconnect the ground wire from the battery, it will hold its charge as normal.

Can anyone advise me how to trouble shoot this. How do I fugure out what is causing the battery to drain?

[Ahsai]

How about connecting a 10A ammeter in series between the battery the the car (via the "+" terminal) and with the engine off and all lights off, check how much current is leaking. I think anything less than 100mA is kind of normal (e.g., alarm).

If it's leaking like in >1A, it could be some light that you cannot see (e.g., the lights inside the front trunk). Now, you can try to pull one fuse at a time to see if that stops the leak. Hopefully with some educated guess, it may not take too long.

Good luck.

- Ahsai

[Moose]

Same issue last year. Turned out to be the front trunk light. I removed the bulb. I also had a bad voltage regulator and had left my radar detector in the cigarette lighter all week, which raised the issue more prominently.

After two fried batteries and a new voltage regulator, I just left the front trunk bulb out. Although an inelegant solution, I generally disconnect the negative lead to the battery, located in the front trunk right in the center toward the windshield, if I'm leaving the car off for a few days.

That may very well mask a battery drain but so be it.

:drive: