Hey guys, i have been having the same issue with my microwave, where the the fan turns on as soon as the door shots. I read all the comments on what might be a potential cause of the problem and still couldn’t quite understand the problem. i found a potential fix while messing with mine, i have a standard 1200W cu whirlpool microwave, if you hold the cancel button for 3 secs it should lock the microwave even if the microwave door is open. And what that does is it prevents the microwave from being functional. you can close the door after you lock the micro wave and then hold for 3 secs to unlock. And that should stop the fan from turning on automatically after the the door shots. BUT my micro wave still couldn’t heat up my food after that trouble shooting. Try this out and let us know if yours heats up your food!! Thanks!!