1986 Kenworth 3406b starter wiring

Hello, I have an 86 Kenworth with a 3406b.

It recently started to have a hard time starting. The starter turns slow. Then today it wouldn’t turn over at all. I checked the batteries with my charger and says all 4 have 12+ volts. I figured it must be the starter.

I put in a new starter and no luck. Still won’t turn over.

I traced the wiring and can’t figure out how the remote wire works on this truck.

I can hear a clicking in my solenoids in the battery box.

I’ve also had an issue with irregular voltage. Sometimes it spike 14+. I’m noticing when I go to start my voltage drops to 10. Let it sit for a minute and it bounces back up.

any ideas are greatly appreciated. I think I have a 12 volt system. At least the starter said 12v on it.

 

Here are pictures of my solenoids in my battery box

 

thank you. I’ve been thinking it could be bad batteries. I might pull them in then go load test them tonight. With that voltage drop makes me think they’re bad.

 

Thanks for your help everyone. I had my batteries bench tested. The voltage was acting strange with a load. Dropping to 9v. So I bought new batteries.

came home and threw them on in the dark and still only getting a click on the solenoid in the battery box but the starter won’t fire.

I can’t seem to figure out the remote wire for the starter. I have two positives that go to the batteries and then there was a loose small wire but I traced it back and it’s broken off. But can’t seem to figure out where that skinny wire would have connected to. There is no wire hanging where it broke off.

 

This is the wiring on the starter. Only had wires going to the positive post and wires on the negative post. I just don’t understand how the starter would get a signal to fire. But I’m almost sure this is how it was wired before the starter replacement.