Your alternator is likely going bad. You can test it if you have a DC current clamp and a meter. You should see approximately 40-60 amps current draw at idle.
My truck doesn't have fusible links between the alternator and the batteries, and the schematics don't show a fuse either. But here's how you could check the alternator cable if you suspect it's bad:
1. Get a volt/ohmmeter.
2. Get the truck to malfunction (not charge, battery light, etc)
3. Measure the voltage drop across the wire. (measure the voltage from the alternator the the positive battery post)
If you have more than a few millivolts, then the cable is adding resistance to the charging circuit. Replace the alternator cable.
More than likely you will see nothing. Measure the voltage at the battery when the truck is malfunctioning. If it's lower than 13 to 14 volts, then the alternator is not supplying power to the electrical system and it will need to be replaced. I usually recommend people recplacing alternators to read my post
Avoid chain parts-store Alternators!!!
The tension comes off the belt by inserting a 1/2" ratchet into the cast-in square relief on the back side of the belt tensioner. Just curious though: how did you get the belt off of the alternator if you don't know how to release the belt tension?
