Manuals for older RVs, well they were not the best, even when new. Your best bet would be to make a list of all the appliances, stove, fridge, water heater, furnace etc. that are in your trailer. Get the make, model# etc and google search for the individual manuals.
I've owned two Bonair popup trailers in the 80s and early 90s. Bonair was a smaller Quebec company that primarily made popup,s before trying the hard body trailers. Bonair closed their doors (out of business??) in the early 2000s.
Gimme Shelter RV, Shelburne, ON , They were long time dealers for Bonair until Bonair's demise. Gimme Shelters owners Keith and Suzy, could probably answer any questions you need about Bonair,
but for most of the RV issues, you will probably get all the answers here. Plumbing, wiring (12v and 120v) is similar in all trailers, just adapted for individual units. Converters, appliances etc are all manufactured by individual companies and then installed in the trailer by Bonair or other RV manufacturer.
Ken