Why would an alternator not be charging a battery?

(2012-02-01 15:20:07) 1. Rave Nation Says: If all of the electrical wiring in a car has been replaced, why would the alternator not be charging the battery? It's a 99 Madza Protege.2. lilnuggy Says: I had same issue once with my 91 mr2 turbo brand new battery and alt but once battery drained car wouldnt run it would just shut off and only thing i could do was either charge it or search for others i found that it was a blown ecu ignition fuse 17 cents not saying thats it but check it out my car had several locations and it happen to be behind a fender in a fuse box i wasnt even aware of good luck and hope this helps costed me almost 400 for someone to fix a 17 cent fuse i couldnt believe it get a haines repair manuel and check or do it visually3. Robert M Says: TWO THINGS!!! ALterantors have CARBON brushes that can WEAR out over time. They usually last for between 100,000 and 150,000 miles on MOST car engines. It is ALSO possible that your VOLTAGE REGULATOR has BURNED up electronics inside. USUALLY, if a BATTERY goes down, it STRESSES out the voltage regulator and it self destructs. AUTO ZONE will test your charging system ffor FREE!!! GOOD LUCK!!4. Len Says: Perhaps it was not reconnected or connected wrong. If you have a volt meter check the voltage of the battery with the car running, it should be about 14 volts and 12 volts with out it running.5. winterle18 Says: Then the alternator is just bad probably just went out or not connected.6. firefighter_joe2001 Says: Because its bad. Happens. Tag: Why would an alternator not be charging a battery?