Battery Light ON, car works fine

[Grand Am]

Hello,
Two weeks ago the red battery light on my 1999 6cyl grand am came on.

Since then, every time I start the car the car, the battery light comes on after about 30seconds.

I did not use the car for a week after the initial battery light came on two weeks ago. After that first week, I turned the car ON, and it started normally, just the light came On 30seconds after ignition.
Since then, I have taken 5 trips of about 80miles each, (400miles total with battery light ON).
The car seems to be working just fine, yesterday I took the whole car to O'Reilly's to have the electrical system tested, it came back as good.
Then I went home, and took the alternator out, took it to different auto parts stores to have it checked and it passed.
I also changed the serpentine belt since I was already there. Today I finished putting it back together and guess what, The light came back ON..........

What could it be???????????????

 

[melsg5]

Check the electrical connectors to the battery, there may be a break inside the insulation. When O'Reilly's tested the system was the light on?

 

[Grand Am]

not sure if light was on during testing, since I was not personally there. Other family member took the car for testing.
Will check the wires.

 

[melsg5]

Well if the light wasnt on the test wouldnt show an issue. Bench testing of an alternator doesnt always show the problem if they spin the alternator at a higher speed than you experience when the alternator is in the car. It should be tested in the car and you can try moving the wires while someone watches to see if the light comes on.

______________________________

 

[Nathan L]

Another quick way to check your battery and alternator is to test the voltage of the battery with the car off and with the car on with a multimeter. When the car is off the battery circuit read around 11 volts. when the car is on, it should be 12 or higher (letting you know the alternator is working). Maybe cleaning the battery and connecting terminals will help. Check the positivewiring to the starter and also to the power distribution box paying attention to any damaged wire or corroded connectors.