So driving home in the dark the alternator light came on . I thought I was screwed as the lights would kill the batt. before I got home .Didnt happen and this morn I tested batt. 12.5 v engine off and 14.5 engine running . But the light is still on . Clamped the big red wire to + post and read 8 Amps .

Why is that light on?

 

I think the voltage regulator built inside the alternator is bad. You have to replace the alternator. Had it happened to me too.

 

Light comes on for over voltage as well as under voltage.

Engine running voltage should be 13.6v at battery.

It does go as high as 14.9volts just after starting, to recharge battery, but then it should drop to 13.6v in a few minutes.

 

alternator light indicates that the alternator is NOT generating any amperage output

that is why the light is on

 

RonD ,thanks for that info I will monitor the voltage again but I'm starting to guess that it is maybe the internal regulator of the alt. as the voltage is reading over 14.4 and I get 3-8 amps with the clamp meter. I don't want to cook the battery . Cheers

 

I have been reading of your problem and I am having the same problem changed the alternator twice. Did you cure yours mine is still a issue