Brand-new-microwave-not-heating-up, my first thought would be a blown magnetron. on microwaves, these can generally go dead, usually with a popping sound. i think there might also be a fuse in your microwave, but i do believe that if it was a blown fuse, your mw would not start up. the technician should also not forget the door... - microwave. Get shopping advice from experts, friends and the community! i have a brand new whirlpool oven/microwave combination model number gmc275prs01 and the oven isn't heating up but micro is. all the lights work including the temp gauge but there is no heat inside the oven.