Battries

You need to check all battery connections first. Check the ground to the frame. Check starter connections. Check each battery individually. Disconnect the wires and do a load test on each battery. Check alternator connections. Check the alternator output. Lastly, just because they were recently changed doesn't mean they didn't go bad. Good luck

 

Also try a parasitic draw test.

 

Find and check ALL your grounds!
Engine to chassis
Cab to chassis
Batteries to chassis
Just because a connection is tight doesn’t mean it’s making a good electrical connection.
Checking grounds on an older truck means completely disconnecting, cleaning and reconnecting all the stacked wires, using a multimeter set on continuity is the final step.
Make sure you have as little impedance as possible, “0” is what we are looking for.
Verify if possible at both ends of the cable in question, it’s not uncommon for an older cable to have a break inside the jacket where you can’t see it.

Some older style alternators have a small wire to the regulator, make sure this is making a solid connection, it is what triggers the regulator.

 

I dunno if it’s an option for you, but keeping a battery tender on when not in use really REALLY helps batteries.

I just changed mine today after 3 and a half years. When the big motor isn’t turning, the generator is, and when it’s home it’s on shore power with a trickle charge.

Interstate batteries, 950 CCA. Less CCA the better - lead plates are spaced further apart than 1000+ CCA, less chance of freeze/heat/warp/ contact.

 

i had to do this a few years ago, tufned out my alternator had a bad diode and was killing my batteries

 

my alternator dont charge either when truck idels very liw on a cold morning, once it gets up to say 650-700 rpm it charges, but lumpin away cold at 550-6 it dont, i dont touch fuel justvwait a minute or 2 it will come up, i also replace all my batteries every 2 years no matter what