Originally Posted by CHICKDOE
so is the gas always on (assuming you tank valves are open)? this would imply that it is not possible to run the water heater on electric only. either gas only or gas and electric. is this correct?
No, this is not correct per se. Here is a tutorial (link below) on the operation (and the 2 DIFFERENT switches for propane/DSI and the electric heating element). Even though it's for the 6 gallon Suburban, the 12 gallon operates the same:
Hope it helps, as this is a frequently asked question and one that is not fully explained in many PDI's with the customer. It's often a point of confusion, hence the very detailed link below.
Suburban's electric switch and much more