97 4-Runner- battery light comes on sporadically- when it does- while running- the battery voltage spikes to 17 volts- assume the alternator is causing this spike? The alternator is the original factory unit with approx 185K miles. ABS light also came on - are they related? Should I replace my alternator?? thanks!!

 

Sounds like either the alt is bad or a bad connection somewhere, possibly bad ground.

Double check the alt, truck running at battery you should get about 14v, should drop a bit if you tun on the brights and put the fan on high but hold stable.

 

checked the wires/connectors- all seemed ok- cleaned up my grounds as well- Battery is 6 months old- NAPA battery- problem still persists- assume alternator as well- thanks!!

 

replaced the alternator! now we have a steady 14 volts at the battery with the truck running! ABS light went off as well!!

 

good to hear

 

Good to know. Alt regulator probably bad. Control circuit was doing its job by sensing over voltage and turning charge error light on, by grounding negative side of that light circuit. IF you look closely at schematic, charge light and ABS or brake error light probably share same negative side with brake error light. That's why you also get ABS error light when you have alt problem. I know its confusing, and I still don't understand why they did that.

 

Could be that people could choose to ignore the charge light.

If the brake error light also lights it might get the drivers attention.

The word here being might!!

 

could be the alternator itself because if it was the IC Regulator, the warning light will not light up because the signal for the warning light comes from the IC Regulator which is where the 3-wire connector is plugged into. The IC regulator is located at the back of the alternator