Here's how my weekend started. On Saturday afternoon, I looked down at the dash idiot charging light to find it on as I was accelerating. Easing up it dimmed somewhat but never went out. I got home and checked all the connections and all was well. I drove to Autozone where I bought the alternator for a charging checkup and they found a bad diode in the alternator and exchanged it under warranty. I installed it and the car started right up, but the charging light remained at 50% brightness. I then shut the car off and tried to restart it only to have it grunt and not turn over. I jumped the battery and it started right up but once disconnected from the jumper car battery and switched off it wouldn't restart. I took the battery out and back to Autozone this afternoon and they said it had a bad cell. The new battery started the car right up and once shut off, restarted with no problems what so ever. But, the charging light STILL remains on at 50% brightness. A couple of years ago, I had re-routed the small wire on the back of the alternator that goes to the gray connector at the firewall, so that's not the issue. I also checked all my wires and grounds to the battery, starter and alternator. All are secure. Where do I go fishing next?
I don't want to kill this new battery, so I'm not driving it until this is resolved.

Any help and direction will be greatly appreciated. Sorry for the long post.
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'86 sedan with 443,000 miles on the original engine and automatic transmission