I have an electrical problem that I have not been able to solve. My headlights slowly dim until they are completely off - the truck then dies. After recharging the battery, I can drive again with headlights for 15-20 minutes before the truck dies again. I replaced the alternator, but this did not solve the problem. I had the battery checked by two different auto parts stores - both said that it was ok. I can't find any obvious problems with any wiring. This is on my 71 pickup (daily driver). I don't know if the problem only occurs when using the headlights since both my drive to work and home was in the dark. Has anyone else solved a problem similar to this? Ideas?