My Norcold 1210IM started beeping and throwing the "no ac" code when in AC mode. When in AU mode it runs on propane even with AC power connected. I have AC power to the control board. With the unit in AC mode and beeping, I have 62v at each of the heater terminals with the heater elements disconnected. Yes I get an HE code with the heater elements disconnected. The resistance of each heater element is 65 & 62 ohms. Sound like a control board?