2017 T660 starting issue

Seems battery 1 is bad or has a load on it only. He needs to make sure all hotel loads are spread across all the batteries not just on one or another.
I would replace ALL batteries at the same time. And if he had a refrigerator and some hotel loads he should get a set of hybrid crank/deep cycle batteries. Some of these are glass mat, some are not. It will depend on his charging system which he goes with .
I also have an onboard inverter/charger.
I have a xantrex, it has shore power connection which powers the inside plugs and also has a smart 55amp charger to maintain the batteries. When I'm home its plugged in. Dont have to shut the fridge down, in the winter I close the curtains and leave the bunk heater on low. The batteries seem to like "working" all the time instead of sitting and I seem to get a lot more battery life from mine compared to others.
Obviously, clean connections are paramount. Once a year I go thru my battery to starter and all my grounds, clean, protect.
Electrical issues can be a bear, good luck, hopefully this helps.

 

Well I will repeat what I always say - CHECK THE GROUNDS - but this time check all of them on the chassis including the alternator.

If you can't check all the grounds, then bring it to the dealer and have them go through it, they know where they are.

This sounds like a ground issue on the battery side.

I also recommend replacing all the batteries in a set.

One other thing, the picture looks like you are using the cheap audio power cabling, you need to secure that so the battery terminal will not rub through it and cause more problems.

 

stick to normal flood lead acid batteries.

 

No. Go to freightliner dealer. They have batteries under 100 dollars... replace all 4 and clean connections then re connect... check all connections to th starter, tighten if necessary... don't overthink it.

 

Pictures, lots of pictures of how they're connected.

 

I have a 17 t660 with a mx13 i worked Saturday all day it ran fine all day no issues then i didn't work Sunday yesterday morning i went to turn it on at it would turn on js crank no check engine lights or anything on the day changed fuel filter it turned on and turned right bk off everything primed as it should checked all fuses and i even tried another ecm and nothing has this happened to anyone or does anyone have any idea what it could be any advice would be really appreciated