ALT light

[thejunkman]

So, let me preface this by saying I'm embarassed to ask this question, as this used to be my line of work. Anyway, I get my truck together finally, put a new battery in, fire it up and the ALT light is on. I test the voltage at the battery. Reading 12.5, so I figure it's not charging. I then jumper the A and F terminals in the voltage regulator and it goes up to 16v. So I figure the reg is bad, go buy a new one and now I'm getting 14.6 which is correct, but the ALT lamp is still on. Any ideas? I repeatedly checked voltage, I checked for dead shorts. Is there another function of the indicator I'm not aware of?

[Thunderfoot]

The circuit that turns on the ALT light is inside the voltage regulator, it grounds the wire for the light on the dash to come on. So either you have a faulty regulator (seen this before) or the wire is shorted to ground somewhere. Try unplugging the voltage regulator and then turn the key to the on position, the light should not light if the wire is good, if it does then check for the wire shorted to ground somewhere.