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Good morning, Well first off if the microwave is completely blank it did blow the internal fuse.Now this microwave actually has two internal fuses, they are located on the noise filter. Now to the cause. the fans starting when the door is opened is a door switch usually. there are 3 of these so you need to test them all. they are marked with arrows on this diagram. numbers 67 and 68. heres a link to a video on how to test them. http://www.repairclinic.com/PartDetail/Micro-Switch/WB24X830/253820?modelNumber=DVM1850DM2BB If they all test good then the smart board is shot. a relay on the board is engaging which means theres a short in the board.