Not charging while driving

[Heath]

Hi all,
New here! Apologies in advance for the lengthy post.

Hoping someone can help me identify what I need to fix or install in my motorhome (2006 Vista Cruiser Mini diesel) to get the house batteries to charge while driving? The house batteries are not being charged by the chassis battery while driving, but they do charge via the solar panels, generator, and on shore power. I assumed this was a battery isolator issue, so I went digging (see attached pics). I found a solenoid in the compartment to the rear of the house batteries (left side of the motorhome), and I verified that I have 12v on each side, one side from the chassis batteries, one side from the house batteries. So then I traced a yellow wire from the solenoid up to under the driver's seat. When I finally found the end of the yellow wires, it was actually 2 yellow wires that were connected to NOTHING. If I cross these 2 yellow wires, the solenoid activates/clicks and the batteries are connected. There is a lot of extra wire for these, so I don't know where they were supposed to end up.

Next to the solenoid is an "Unknown Component" that uses one of the mystery yellow wires, along with ground and a connection to the solenoid.

So, my questions are... What are these 2 wires supposed to be connected to? Some sort of battery isolator/relay? If so, is that supposed to be under the driver's seat?

Or is the solenoid I'm looking at strictly for the AUX start? The AUX start on/off switch has 2 orange wires that also go under the driver's seat. One goes to the chassis 12V+, and the other I can't locate without taking the driver's seat off. The AUX start also is not working, so I'm not sure if these are just two related issues with this solenoid, or if I should be looking at a ground issue for the charging while driving problem.

Thanks in advance for any help!