I would check underneath the panel above the breaker box on the passenger side where the bed is. There should only be four screws to remove and then you can lift up that panel. You will also need to remove that if you choose to winterize the coach because the valve to turn off the fresh water tank is over there. I had mine off but can't remember if the shunt is over there but worth checking. If you can't find it would probably just call Thor Customer Service. If you don't already have their schematics for all things on your Tellaro check the following link and register and you can download:
https://thor.mizecx.com/login.html#sblox=knowledge
Also, if you have not turned off the master rotary battery switch located below the Balmar would try that first after making sure the coach is not connected to shore power.
Good luck