2015 Prostar voltage issues, fluctuates between 13 and just under 14

Have a 2015 voltage keeps fluctuates between 13 and just under 14. Usually it sits at 14.2 to 14.4. I have replaced the batteries and alternator and still same problem. Replaced fuses to battery box leafs coming from batteries this morning, still same problem. What could be the problem?

 

I actually don’t have one on me, but where my load is going to I can get one. After posting this question I spoke to someone who said that same thing to check connections at the starter. I have cleaned the main cable connections. Yesterday the body controller crossed my mind.

 

It’s kind of weird that when I’m sitting idling it shows normal but then when I get moving it dips down to 13.5 or so

 

Ok that makes sense....

 

Hey quick question.... I’ve heard you work for a International dealership so I was curious. What do you think about Fleetrite batteries? I just got these new for the International dealer in Phoenix. Is it possible they aren’t the correct batteries for this truck?

 

Will do thanks for the information