I finally had to replace my 1981 battery, I had no warning lights or issues except one morning (didn't drive it for a few weeks before) it just wouldn't crank.   I put in the new battery and when hooking up the negative termal on the disconnect switch I heard relay "chattering" until I got tight.  The battery idiot light was on as well as the interior light under the glovebox. 

If you had the door open while connecting the cable, then courtesy light would have been on anyway.
The battery light will be on anytime the key is on, but it shouldn't be on with the key off...
The courtesy light coming on could indicate a problem with the timer, but....it shouldn't just come on when you stop/turn the key off...it is possible, tho.
Make sure your ground cable from the batt to the frame is in good shap, and making good contact on the frame. Then check the ground cable from the frame to the engine at the front, by the engine mount...

Thanks Joel - I'll keep you posted.  Doug

Doug,

I checked the grounds and the fuse; all seem OK.  I then unplugged the alternator 2 prong plug and the problem went away.

Does sound like an alt problem. Ya might take it off an have Pep Boys(or some other place) check it out on a machine first. If you have the service manual, there is info in there on how to test the various components. Ken could tell you/us the procedure, but I'd have to look it up and post it.

Just out of interest, what type of battery did you get for your new one ?

Finally completed the repair.  It took awhile because I searched for an alternator with a date code a few months before my 10/80 build date.  Found the alternator but it was in bad shape; I had it rebuilt and restored.  Installed and it finally works great.

Good to hear!!