Battery light illumination

[krazy13]

Ok... I cave. After weeks of trying to figure this one out I have to ask the car gods.

Here is the deal. I have a 91 s13 se. I have replaced the battery and alternator with new ones. (starter was also recently replaced and the previous owner is... "special" didn't remove replacement nut to put on new starter.) When I drive at night with my headlights on the battery light comes on. I have been checking the connections to the alternator and battery to ensure that everything is on correctly and everything is snug. So anyone have any idea why this is the way it is? Do I need to tighten the alternator so the belt has less slack because the slack on the belt is about 1/4 to 1/8 inch of free slack. Thanks in advance.

[rwtf]

did you test the voltage while running.............?

[kingJurzy]

Agreed with above. Take a volt meter and test out the voltage at both the alternator and the battery.

[starplatnumm]

Check if there's an o ring on the alternator harness socket. Most likely the o-ring denigrates over time and does not retain in the alternator. Check if its loose fit.