This is a point that can get really difficult if we are not fully plugged in and a bit obsessive about following the trail!
The big problem is getting the right info together and knowing that we are following the correct trail as we have different builders and they use different methods on their drawings.
Big secret is that there IS no one specific way to do drawings and they often vary, even within a single industry! Winnebago does give us drawings for the part of the wiring they add to connect the propane furnace to the thermostat which is then connected to the air unit with heat pump!
But that can leave a big void when we need to find the info for the Suburban propane furnace, the thermostat from a different and yet another company builds the AC/ heat pump!
The picture BigB has posted above is a hint at what can become a major problem if we are not really careful! Take any one of those wires and then decide if it is going to be connected to the same color on the plug it meets if a different person plans and installs each group of wires?
Since we have the Winnebago drawings, I start there on looking how this is wired.
Click this snip to see what I mean.
We can find the furnace fuse and see it starts out on a 14 gauge yellow for 12VDC battery. That leads to the thermostat and furnace plugs and we can see the ground comes in on a 14 white to a plug for thermostat and another for the furnace.

So what color wire did the folks who put the plug on each of those use?
We have to have the drawings they use OR we have to dig the plug out and look at what they did!
We can see if battery and ground get to the plug on the furnace and thermostat but we need to look more before we can say it comes back out where and when it is supposed to do it!
That is where I begin to favor working on the propane furnace first as power goes there, THEN to the thermostat before finally going to the air and heat pump.
If none of the three work, the furnace is where that power first comes from the fuse, so I would want to make sure it gets out of there to the thermostat to make that furnace run.
I would follow the path like this:
Fuse to furnace where we need the drawing for the furnace brand and model we have, then to thermostat (different drawing for it!) , back to furnace and finally back to ground.
If I can get the simple one to run, maybe it fixes the really hard one in back and I avoid beating my head on that bigger rock!
