You might need to call Heartland Customer Service at 877-262-8032 / 574-262-8030. Have your VIN # ready. The early Yeti package had 110V AC tank heating pads and thermostatically controlled 12V DC heat tape on the main water line. One issue was that even if the big light switch for the pads was OFF, the heat tape could call for 12V DC power any time temps dropped - draining the battery.
I'm wondering if maybe the big switch now operates the tank heating pads, and a relay that powers the heat tape. That would let you turn both on and off with a single switch and avoid the battery drain if dry camping in cold weather.
If Customer Service can get you an answer, please let us know what you find out.