I agree...the headlight motors.If you can (on your day off) disconnect the single power wire to the right and left headlight and see if the battery holds a charge.Dont leave your battery flat too long, or you could kill it.Try the mall section and upgrade to 87-88 headlight motors.You will need everything from the 87-88 headlight system includeing the wireing harness and modual,that detaches at the front firewall.Other causes are:
1.Trunk light on.
2.Out of alignment brake pedal switch causeing your brake lights to stay on 24-7.
3.A bad door pin switch, causeing your courtesy lights to stay on 24-7.
4.A stuck fan relay,causeing your fan to continualley run (but youde probubley notice that).
5.Electrical...an example would be if you had an alarm,but say lost the remotes,so you removed the horn and the alarm was triggered and active 24-7,even though you can't hear it.An improperly installed AMP would probubley do the same thing.
6.Acid on the contact sides of the battery cables,preventing the battery from chargeing.
(your charge gage on your center dash should read about half way with slight fluctuations).
[This message has been edited by James Bond 007 (edited 06-27-2008).]