Are you saying that when you turn the salesman's switch on, you get no power to the other circuits? I think this switch actually controls a relay. The place to look is still the compartment under the driver's seat. If you can't find the card identifying the circuits, by all means give Tiffin Service a call.
Roger & Mary
2017 Winnebago Navion 24V (Sold)
2014 Tiffin Phaeton 36GH (Sold)