2006 LBZ "battery not charging"

[lucas6.6]

Truck began showing this message last night when I noticed the volt meter was well below 14v. My initial thought was a bad alternator, but the light does not stay on consistently, it will go off every now and then and the battery will charge for a short period of time. Unless that would happen with a bad alternator, what else could be the problem?
Thanks

 

[malibu795]

Check juction box where the alt wire hooks to the power block
What condition is the belt in? Old belts can slip without noise

 

[lucas6.6]

Junction box looks fine, no corrosion or loose nuts, belt also looks to be in good shape

 

[malibu795]

Check plug to all. Should have a ground and a switchable hot to charge the field to turn the apt on

 

[E.carter]

Unhook the batteries and load test them. I have seen this issue in the ag scene with dual batteries and one going bad.

 

[malibu795]

Unhook the batteries and load test them. I have seen this issue in the ag scene with dual batteries and one going bad.

Or is bad and internally shorted