Hi Mike and Welcome to the Forum!
It should be very easy to identify the chassis make. Look at the middle of the front grille. Bowtie for Chevy or a blue oval for Ford (or possibly Dodge but I think they were out of the RV game by then). Same thing on the center of the steering wheel.
Don't bother finding an "Owner's Manual" for the coach. They usually contain very generic information. Start finding the identification tags for all the appliances and systems, Furnace, fridge, water heater, etc. You should be able to find those service manuals online. This web site should get you started.
Service Documents and Manuals
Depending on what chassis you have under that coach you can probably find an Owner's or Service chassis manual online too. Look for the van chassis manual.
Sorry, but I don't have any obvious answers for your charging problem other than to check and clean ALL connections. Then try to temporarily bypass extra wiring and isolators, etc. to get it down to basics (battery & alternator only) and see if it will charge.
Best of Luck!