Sorry, I don't know how it is accessed other than it will be exactly behind the outside HWH panel, except on the inside of the coach. I see that you are relatively new to the forum so I will share a piece of advice that I rec'd here that has helped me with these issues:
Go to this link:
https://www.thormotorcoach.com/owner-login/
Register with your VIN and then go to the list of documents. There is a drop down menu with "schematics" listed. See what is in there. If there isn't a lot of electrical and layout drawings, then send Thor an email (not chat) with your VIN. Request all schematics they have on your coach. Wait a week or two and you should receive them.
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