A volt-gage can tell you a couple more trouble shooting things that a light can't, but point conceded.
For one, if the needle dances at idle, that can say that half the rectifier diode group (inside the regulator module) is out. On the average that is important only once every few years.
For one, if the needle dances at idle, that can say that half the rectifier diode group (inside the regulator module) is out. On the average that is important only once every few years.