I have a 1997 mercury tracer (manual) and 2 days ago I could not start it because the battery was too low. I jumped started it but when I removed the jump cables, the engine stopped 2 minutes later.
I realized that the battery light on the dash board is never on anymore. I checked the light bulb (it was fine) and replaced it anyway, but it still doesn't work.
I did some measurement and found out that the battery voltage was low (about 12V) and that also the alternator wasn't delivering anything (I believe I should find about 14V out of the alternator).
I read few things online, and my understanding is that when I turn the key to start the car, a 12V current light go through the battery light and wake up the alternator.
So since the battery light doesn't go on, I'm not quite sure that the alternator is the problem. I don't know how to find out what is the cause of the problem with that light.