I've been having weird issues with battery dyeing in my '07 997TT. The issue is completely intermittent. I can be driving the car all day and next morning the battery will be dead. Inversely, I can leave it parked for a week, and it will work just fine. I can’t find a pattern. A symptom (or a cause) is the passenger airbag light comes on, seemingly before the battery is dead. This makes sense as I am told battery under volt is one of the things that will trigger the system to turn off.
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</o> I took the car to my dealer multiple times with this issue and they just can’t figure it out. They replaced the battery, put load testing equipment on, etc. Everything seems normal. Yesterday the battery died while in the shop. I was hoping that would give them enough info to find the problem… but nope. Everything is normal today after they charged it up. Pulling my hair out trying to figure out what else it could be. Any suggestions on how to even troubleshoot something like this? I think my dealer would appreciate some help too. Their next step is to submit analysis data to Porsche and see if they have any ideas. This doesn’t sound too promising to me.

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Wiring harnes short. I had one that caused me issues when the car only had 100 miles on her. It took three weeks and a nwe engine wiring harnes to corrrect.

 

Alternator +/- a short in the system.