This is your isolator assembly - And where your solar connects to the batteries to charge -
The upper left is the isolator delay relay - Blue wire goes to the ignition source, Red and Black go to your isolator solenoid to do the switching between main and aux batteries, and the rest is just protection in the form of fuses and circuit breakers.
Do you happen to have a toner(Wire tracer) avalible? There should be a small box before the "solar panel" fuse that is the charge controller. The whole setup should go as follows -
Solar Panel Leads +- --------> Charge Controller --------> Solar Panel Fuse --------> Battery Bank
Diagram --> http://www.backwoodshome.com/articles2/images/yago93-4.gif (You may not have the load terminals on you controller, but you will have solar +/- and battery +/-)
I would think that the controller would be out of the elements, unlike the panel in the picture.
The indicator light that you usally see when the solar is functioning correctly - where is it located? On the panel that gives you status on your battery power inside the MH, or is it independent?
You have located all of the connection points - Input(Solar Panels), Output(Battery Bank/"Solar Panel" fuse), and Indicator lamp. All of this stuff will tie into a common component which will be your solar charge controller.
Give me a call(702-525-7525) when you have a few minutes in front of it - it might be easier to locate it that way.