1986 Kenworth LW900 Dump...Battery Wiring help

Here's a diagram of a Delco Remy series parallel like yours. I've done allot of this work in the past, but it's been awhile so I need a refresher, but I could probably help you get it together and working if you like.
http://www.texasindustrialelectric.com/images/relay_1119845_wiring.gif

 

Two six volt batteries in series would equal one twelve volt in the link you posted, correct?

 

That's correct, when you take two 6 volt batteries and run a jumper from one pos b+ of one battery to neg b- of the other battery you have made 12 volts from two 6 volt batteries. You do this to two sets of 6 volt batteries and you now have two independent 12 volt sources that are joined through the parallel switch.

 

Bender I would have him give you a better picture #1, I don't think that is a series parallel, it is hard to see very well, even at that, they should be twelve volt batteries, no matter how you wire it, if your going to run it in the winter much. I don't remember any of the manufacturers using six volt batteries as far back as ninteen seventy three anyway. They did in the sixties.

 

In the picture #1 I can only see one cable going to the solenoid, should be a minimum of four if i remember correctly, and I think the diagram you posted on the link shows what would be four cables. The starter will have a tag on the body of the starter telling the voltage twelve or twenty four as well, if you can get focused on it while it is installed on the engine.

 

On our t800, we have 4 cables connecting the solenoid.

 

First things I see is the battery cables, bolt on connections are junk, Period. soldered connections are what you want. You can Google a series Parallel switch and get pictures.
As stated, first turn the motor over at least 4 turns, Series parallel systems work but not very well at the best of times, Two batteries will over charge and two will be undercharge. You want to test the isolation switches for any resistance, a small resistance will hinder both starting and charging.
I would be buying new battery cables or ends, Putting the system to straight 12 Volt is a lot easier, and having to get towed once because the system breaks down will fully cover the costs.
Just a thought!