Welcome to the forum
Let’s see if we can get to on the road to successful ownership. There are no schematics available to anyone even the dealership and is techs. We have to use meters and test lights.
You can remove a breaker and take it with you to the local big box store and simply match it up. They are not RV specific.
If the furnace is lighting then the blower motor is working, can you locate it, take off the return and look for the “box” (plenum). Look for flexible hoses not hooked up, and if they are it’s time to look under the trailer for missing or ducting with holes.
Maybe start a different thread for the fridge and water heater, that way members can reply to one issue at a time.
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2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.