pitr

So for the last month or 2 the GEN light on my 97 12v has been coming on from time to time, but the volt meter in the dash was still showing it making power.
2 nights ago it fininally died all the way, 0 power. I assumed it was the regulator in the PCM so I swapped it out with an external unit. Still nothing. Pulled the alternator and took it in, it was dead. Swapped in the new one but decided to stay with the external regulator just to avoid future issues and since I already had it all wired and ready.

The problem is the GEN light is still coming on, then going off, then coming on for 5 minute, off for 8, etc, etc. The meter in the cab shows voltage as what I think is a bit high, 15-16, but when I was testing with a real multimeter the in cab meter seemed to be reading high.

So:

What voltage should the alternator be putting out at idle?

At 1500ish RPM?

How much voltage is overcharging/should I worry about?

Does anyone know how exactly the PCM decides to turn on the GEN light?

Thank you much,
-Matt

TIMMY22

13.5 to 14.5V

anything over 14.5V for a prolonged period will quickly ruin your batteries.