Hello John
My '06 Monterey has an Aquahot, but does not have the engine preheat circuit, as that was an option on the Aquahot. If you have a rocker switch labeled "block heater" or similar (mine is on the panel that the transmission controller is on) then you most likely have an electric block heater. On my coach the cord, and plug, for this function is under the bed.
Brad Burgess