1999 Ford ranger charging problem

I just had a battery go bad and replaced it. Now the ranger only charges 11.9 volts. Does anyone have a diagram of the charging system. Was told a battery going bad could damage a alternator
Thanks

Thank you. Is it possible to have a good alternator charging 2 volts low from bad battery connections or corroded connections at alternator. Does voltage at I terminal turn regulator on and off?

Sounds like a voltage drop issue. You have a multimeter go from battery negative to alternator case should see below .2 of a volt. Then go from battery positive to alternator battery cable stud. Should see below .5 Volts

Carfreek wrote: Is it possible to have a good alternator charging 2 volts low from bad battery connections or corroded connections at alternator.

I would say "Not likely". Someone will correct me if I'm wrong. If you had a bad/corroded connection at Terminal A (YEL/WHT), you might see less voltage than the alternator is really producing.

Does voltage at I terminal turn regulator on and off?

No. Terminal "A" (YEL/WHT) is the voltage sensing circuit. All the "I" terminal does is control the warning light in the instrument cluster. Power comes from the battery, through fuse 15, to the warning light. When the alternator is charging, it also sends power to the bulb on the "I" terminal (lt grn/red). Receiving power from both sides (the bulb), the difference in potential is near zero, so the bulb does not light. But when the alternator is NOT charging, The "I" terminal will be near zero volts (ground). Now, there is enough difference in potential across the bulb for it to light.

Are you talking about this specific setup? Or is it possible for any alternator to not charge from connection issues. That’s what I thought you were asking

My truck has the volt meter in dash no light

Cheryl wrote: Sounds like a voltage drop issue. You have a multimeter go from battery negative to alternator case should see below .2 of a volt. Then go from battery positive to alternator battery cable stud. Should see below .5 Volts

I would test as Cheryl suggested. If you have no voltage drop, and the system voltage is low, it is safe to say the alternator is not charging. Check for battery voltage at Terminal "A"