What Causes Alternator Not To Charge Battery. The test is able to determine if the charging system is not working or working at a limited capacity meaning the alternator isnt able to provide enough charge. In theory a car can run only with the alternator charge but this can cause heavy voltage spikes and other strange symptoms so this means that a bad car battery can cause an alternator to not charge also.
If the charging system did not pass the test your mechanic needs to do further tests to see if the problem is the alternator not charging or if another mechanism is the source of. Tested Battery as OK. Did a Alternator test at 2000rpm and the meter said not enough for charging.
Other potential problems are a faulty voltage regulator or a problem in the charging system wiring.
Turn it to dc volts put your leads on your battery with the car running if your alternator is charging it should read from 135V-145V thats a good charge. There is a parasitic electrical drain on the battery possibly caused by a bad alternator. On the other hand any number more than that indicates its overcharging the 12V battery. Using a multimeter you can test battery power.
