My two cents....
I have a 2000 NBS with 197,000 miles and have replaced about 5 alternators and only one battery over the last 10 yrs/150,000 miles. Sounds to me like the alternator. I purchased a reman unit with a lifetime warranty so technically have only purchased one alternator and the rest were replaced for free. You can have the Parts Store test both the alternator AND battery while on the truck, no need to remove them. Depending on how far of a drive you have to the Store you could trickle charge the batt over night and the attempt to drive the truck up there for testing. If its too far take the parts up there, the alternator is easy to remove and so is the battery. Theses trucks need a lot of juice to run right since everything is electronically controlled. The battery may still take a charge so all you may need is a charge and an alternator. Hope this helps, btw, I don't have a boomin system so the lifetime warranty is a must or you'll break the bank over the next few years on alternators.
