I have a 98 1500 5.7 L 2 wheel drive, new battery, alternator, checked all the cables, used a jumper from the alternator to the battery, had the alternator benched tested, battery light comes on when the ignition is turned on then goes off, but the alternator is still not charging. I read a post that said it could be the wrong alternator a 130 rather than a 130D or the brown wire from the alternator to the instrument panel, I’m at a loss, all ground worse check out,
What is battery volts before and 5 minutes after engine start?
Check for voltage at the large wire on the back of the alternator with the engine running. It should read 14-14.5 volts. Now check if the same voltage is read at the battery. If not the fusible link in that large wire is probably burned.
While the method is not iron clad, you might turn the key to the RUN position (engine off) and touch the tip of a screwdriver to the alternator pulley.
If you feel a magnetic attraction on the screwdriver tip then odds are the alternator is good and the problem is likely what Tester mentioned.
The battery warning light is working like it should be under normal conditions and it is important that it does since current throught the lamp provides power to the exciter inside the alternator. From what you say it sounds like there is a bad fuse or link for the output of the alternator or a bad connection to the output. Check the output as @Tester suggested.