Battery / Charging Light Issue
 

2001 Boxster S 64,000 miles.

I have a battery/charging light come on the dash 30 seconds to 1 minute after starting the car. The car runs a bit rough when this happens. I'm hoping someone here can help me troubleshoot as I'm running out of ideas. Details of what I have done so far below.

I read as many posts through Search as I could but haven't seen this particular issue from someone else.

I first checked the battery, it was old so I replaced it. Starts better but that's about all. Didn't change the situation any.

I also checked voltage across the battery terminals while the car was running and it's not as high as it should be. It's normally between 12 and 13 volts.

So that made me think it was the alternator. I pulled it over the weekend and just had it tested at a dedicated alternator and starter shop and he said everything was fine. He said the clutch felt good and with the relatively low mileage the brushes should be no issue.

I have a spare voltage regulator I bought a long time ago, but this doesn't sound like the right issue. From what I was seeing, the VR issue causes high voltage and fries batteries.

I saw in one post there was a question about the "Y connector" cable that goes from the alternator to the starter. I don't know the history of that issue and couldn't find it in search. Thought I might replace it while I have everything pulled out.

The ignition switch feels ok at the moment, I've replaced it twice already.

The only other issue I think I have at the moment, that isn't a rattling trailing arm, is an AOS in the somewhat early stages of destruction.

Any help and advice is appreciated.