Yesterday, AC clutch quit engaging almost home, got home shut off no start just clicks checked batteries low
Charged batteries, started checked voltgage on drivers side 12.3
Went to advance warrenty swapped alternator
Started truck checked voltage still 12.3
My sons 6.0 was here and checked his 12.3 also
Brain fart finally checked passenger side 14.9 on mine and his
Is this normal ?

 

disconnect and check each battery separately (engine off ) a dead battery will kill the other BTDT. Next go thru and check all connections and grounds

 

No, that's definitely not normal. Heck 12.3 is low even for a battery at rest without any load on it it. I would start with what's already been suggested. Chances are you'll find a bad connection between batteries or ground. May want to give both batteries a good long trickle charge separately. Hopefully that will bring them back and they'll be in sync. Any measurable difference in voltage and they will be fighting each other Thunder Dome style.

 

14.9 is a little high but I don't think that would worry me. I would expect them both to read the same though. You are talking about while running, right?

 

If the cables between the batteries and the associated cables, connectors, lugs and points are in good condition, the batteries should read exactly the same voltage.

 

thanks all
Ill do some more checking

 

Check for voltage drop at various points. You can check between the battery post Alternator charge post, then break it down into segments. Battery post and cable end, between each respective cable end and the next one in line, From negative post or terminal to alternator case.

Any voltage drops more than 0.0 are suspect.

You can do the same test measuring resistance. I usually try to get everything below .2 ohms. Less is better.

Alot of times just cleaning battery posts and terminals is enough, though these trucks are known to develop corrosion inside the crossover cable on top of the radiator.