alternator ?

96 s 10 that when rpm's increase the lights get brighter and dimmer as rpm drops. Volt meter in the car follows the same pattern. Any test I can run at home to narrow possibilities :disappoin

it sound like the voltage regulator is going out ( which is in the alt )

I agree with Smokey. Have your Alt rebuilt. it's just as good as a new one, and much cheaper. My brother rebuilds them and tells me it's just a matter of swapping out brushes/bearings and a few other small pieces. I'm not sure exactly what he changes, but it works, and he says it's simple (if you know what your doing) If you take it to get rebuilt ask them if the change the volt regulator.

Where I live there is an auto recycler where we can go choose the parts we want on the car, and pull them ourselves. I can usually find just rebuilt starters and alternators for less than 1/2 the price of rebuild kits

be careful on going to the junkyards unless you know the alternator that will match with your. there are about 8 different regulators for the cs130d.maybe 2 of them will work on the truck. one of your diodes are blown. they are easy to fix if you have the right tools.