You didn't list any symptoms now after the generator was replaced. The battery is likely still okay, so leave that alone for now. The old generator from 2013 worked okay for two years, so replacing the battery the next day was good enough to avoid another generator failure. The failure now was just "the nature of the beast". Every GM owner replaces their generator two or three times if they keep the vehicle long enough.
My recommendation now is to have the charging system professionally tested by a mechanic, not at an auto parts store. In particular, what I want to see is "regulation voltage" between 13.75 and 14.75 volts, full-load charging current very close to the generator's rated value, and "ripple voltage" should not be excessively high.
The common generators for your truck were a 105 amp, a 124 amp, and a 140 amp unit. Full-load current will be very close to one of those values, or, ... If there's a defective diode inside the generator, you'll get exactly one third of that value. A generator is physically incapable of developing more current than it's designed for.
If ripple voltage is high, that is caused by the generator developing harmful voltage spikes, but it's the job of the battery to dampen and absorb them. Consider replacing the battery if ripple voltage is high/
Friday, September 25th, 2015 AT 9:24 PM