I was having similar issues with locating the winterizing/antifreeze inlet on my Quantum. After posting a few questions I took someone's advice and registered on the Thor Owners Resource website and was astonished as to the vast amounts of info, schematics, and drawings listed for my coach. On the schematics tab I found the exact location of the antifreeze inlet and valve for my coach. All you need is the VIN number of your coach to register and all information pertinent to your model is listed to view and download. I filled a 3 ring binder with info and it is now permanently stored in the coach for future reference.
A virtual gold mine of info.
Here is the link:
https://www.thormotorcoach.com/owner-resource/
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