Mr Carlson’s Lab had a defective Magnum Energy MS2012 Inverter Charger. When powered up the remote head unit indicates an Internal NTC fault. This fault indicates a temperature sensor fault issue. By looking through the diagnostic menu he could see that the system thought the FET temperature was at 151 degrees C when it was just powered on and should be reading room temperature. Carlson goes through the process of getting the unit working again.