Hi, im new to the board. I have a beautiful 1984 720 4x4 5 speed Z24. She's pushing 265,000 miles and has been strong the whole way. Nowadays she's got some electrical issues that are becoming problematic. The main issue is that the battery is not being charged by the Alternator but both are good. Before I get into that some smaller issues that are going on I will share in case they could be related. Let's see, when I start the truck there is a series of beeps that sound off each time. Well they are suddenly delayed. They won't happen at all or they will randomly sound off after ten minutes of driving. Sometimes they will sound off and continue sounding off until I can't take it anymore and just stop driving. When I turn my headlights on the brights illuminate. I have to wait several minutes and/or flicker with the switch to get them to go back to the low beams. And when I do switch the brights on intentionally, there is the same type of delay to get them switched back off. For a time the headlights would cut out completely while driving and I would have to turn the switch off and back on, sometimes multiple times to get the lights to illuminate again. Let's see, also my left hand turn signal is sensative. If I hold the indicator switch to the point where it engages the light it works fine but if I flip the turn signal indicator all the way to the point that it locks into place it will not activate the blinker. Other than that my fuel gauge is confused. It's either not working at all or reads as full the whole time. Also my pickup use to get 250-300 miles on a tank of gas but for some reason these days it wants to act like its running out of fuel around 200-220 miles. But finally my immediate issue, my battery is not being charged by my alternator. I recently replaced my Alternator as the battery light came on and my battery drained and I tested the Alternator and it was low output. Since then the truck runs fine for as long as the battery takes to drain and then it obviously has issues. I am swapping out 2 different batteries and they are not the issue. However the truck runs without the battery connected and the Alternator seems to be working fine. When I test the battery with a multi meter it's 12 volts and when the vehicle is running it's about 13 volts. Maybe a little over is this enough? However when I turn the headlights on while the truck is running the voltage drops back down to 12. My battery definitely loses its charge mostly at night when I'm using the lights. I don't understand why my Alternator will charge the battery at 13 v but when the lights are on it will not. Can this be the result of the belt not being tight enough? I apologize for the length of this post but I wanted to get as much info in as possible. Any advice? I'm running out of ideas.

Also I did just now notice that the tiny wire on the Alternator that runs to the condenser was looking kind unhealthy and wiggled on it a tad bit and it broke real easily. Would that wire being bad or broken effect anything? I'm unsure of its significance

If you are only getting 13 volts coming off the alternator, then there is a problem with the alternator or the voltage regulator. I believe the regulator is inside the alternator on '84. You should see at least 14+ volts coming off the alternator. When you turn on the lights and the alternator voltage drops to 12 volts is a big sign that the alternator is the problem