Help with 5250 electrics, identify this?

[Microguy]

I've got a couple issues. Just really trying to figure out what we have. First of, the truck alternator doesn't charge the coach when the engine is on. So I was tracking down the isolater. Still can't find that, the power cable runs from the truck battery back to the coach batter compartment and no isolater.

But I did find this part, which I'm assuming is the emergency start relay, which also doesn't work. Big starter solenoid/relay, coach battery voltage on one terminal, truck battery voltage on the other. All it does is buzzzzz when you press the emergency start switch.

Anybody have any idea where the isolater may be located? And is it an actual "relay" system as opposed to a dual diode solid state type?

Like I said, I tried tracing the power cable out, but it goes straight back to the coach battery compartment to this device, and does a bit of looping, and after that there's no telling. Very hard to follow where anything goes.

Any help on this would be much appreciated, but actually we can live without it as long as everything is working.