Nissan Repair: battery light showing (faintly) on dashboard when driving, competent mechanic, high beams

Question
i have a nissan primera M reg, about 10+ years, recently when i was driving the car just stopped on me ans the battery light on the dash board was showing. iv tried relacing the old battery with the new 1 but it didnt make a difference soi but back the old one in. when i try to start the car, sometimes it doesnt.
could you help me with a solution

Answer
Hi David -

Have your alternator checked. I do not think it is charging the battery. You need to have an output test, and a load test done on it. Take your car to a competent mechanic and have this work done.

You can do the output test yourself with a voltmeter, by placing the leads on your battery. Should read 12 volts. Start the engine and notice voltage again, should read 13 - 14 volts. Turn on the high beams for your headlights, and voltage should stay steady at 14 volts. If not, replace the alternator.

Hope this helps -
aloha
calvin