I was listening to the car radio while I was doing an oil change and some other stuff for about an hour. That was enough to drain the battery, so I was unable to start the car. I used a charger to charge the battery.
A few days later, I checked the voltage of the battery while the engine was running, and I got 13.8V. The other car I have, which had a new alternator put in about 30,000miles ago showed 14.2V - 14.4V, when its engine was running.
The car is 2003 Crown Victoria with about 100,000 miles.
Do I need to replace the alternator?
Is 13.8V high enough to charge the battery in most normal conditions including running high beam and rear window defroster at the same time?
Does the alternator degrade over time (with charging voltage slowly falling) until it completely fails, or does it fail like an electronics product?
I searched the web and found some saying the minimum alternator charging voltage is 14.0.