Charging system suddenly not working
 

My wife and I took our '03 Boxster S on a 300 mile round trip today. At almost exactly the 1/2 way point, on the top of the continental divide in Rocky Mountain National Park, I pulled over at a scenic overlook and the car would not restart when I was ready to go. Just clicked rapidly and the dash lights would flash on and off as it clicked. Luckily, I was able to roll start it from where it was parked and drove it all the way home without shutting it off.
As I got close to my house I put the top back up and it barely made it closed. You could hear the motor for the top was running very slowly. As soon as I got home I put a volt meter on the battery terminals while the car was running and it showed 10.71 volts. Then I shut the car off and it still showed 10.71 volts.
After partially charging the battery, it now shows 12.46 volts, I'm still charging the battery so I haven't started it again, but I know it's not going to show a charge from the alternator. I called my mechanic and he says likely the alternator failed, but will check it out tomorrow. He said he can't believe I was able to drive it at least 150 miles without an alternator and with it showing that low of voltage by the time I got home. I feel extremely lucky that I was able to get home. Thank God it wasn't at night as I'm sure I wouldn't have had enough juice in the battery to get back.

The car only has 32,000 miles on it (I've owned it since 2008). I get that it is starting to get old, but is it common for the alternator on these to go with that low mileage? This is the very first time anything has actually failed on the car. And, there was no idiot light or other indication when the charging system failed, so the first indication was when the car would not start. Is that normal?

Glad you made it home safe!

I agree that 32K miles is not a lot on an alternator but things do happen.

Right now, you haven't really determined weather your culprit is the battery, a connection or the alternator.

How old is your battery? Is the water level correct (no such thing as a maintenance free battery)?

Need to read the output voltage from you alternator, as you mentioned.

I wouldn't loose confidence in your car from this incident, nor would I expect other wear and tear item to fail.

I feel pretty confident from my voltage tests with the car running and off, that the alternator has completely stopped working. My battery was all that got me home, so it's doing better than I thought it would be as I planned to replace it as a preventative maintenance item this season. It's about 8 years old.
The car is going to my mechanic tomorrow so we'll see what happened.

Buy one of these and keep it around, not a replacement for a true system check out....but will tell you a lot quickly for 7 bucks

New Easy Quick Battery Alternator Tester 12V 12 Volt System LED Cars Trucks | eBay