Yes, the red tank heater switch turns on the heating pad on the fresh water tank, the black tank, and both grey water tanks.
Since your unit is a 2012 model, Iím guessing you just bought this RV used. If so, there is a high probability that your water heater is still in bypass from winter and there is no water in the water heater. Easiest way to check to see if you have water in the tank is to open the pressure relief valve. If water comes out thatís good, if no water comes out then you donít have water in the tank.
Hereís a link to a post that shows what position the valves on the back of the water heater should be in for normal operation. De winterizing for the first time and need help.
Look at post #6 for an image. That image also shows what position the valves should be in for winterizing the Silverback.
BTW, if there is no water in the water heater and your turned on the electric element you probably ruined the element and you will have to replace it. Your water heater should still work on propane though.