i was wondering if its time i replace my alternator. latley under the hood its started to make a humming/howling noise. and increases with rpms. ive noticed on my voltage meter on my radar detector that on idle with my lights off i read 13.8- 14.1 volts. when i turn on my headlights it drops to 12.4-12.8 and with the heater on it drops as low as 11.8-12.2 then with window defroster and wipers the low voltage warning on the radar dectector comes on. no battery light on dash tho. is this normal. it dosnt seem as tho it is. i dont recall my voltage dropping this low with accesories on. when i drive or raise rpms the voltage goes back to 14 range. sometimes after all the accesories being on after a short trip it takes a bit to start the car again like the battery is drained. any sugestions. i think its the alternator. perhaps should i upgrade to a high output while im at it?

xwizkidx, you can try unplugging the negative of your battery while engine running to see if the car would stop running...

I just replaced the alternator on a 1993 altima outputs 16 volt with and without the battery connected. After installing the new one, it still outputs 16 volt...

Does anyone know what else could be wrong? I thought it was the voltage regulator inside the alternator but I guess not.