Whirlpool microwave oven carousel spins continuously

We have a Whirlpool over-the-range microwave that’s about 10 years old. The model number is MH1160XSB-5, manufacture date of Apr 2008. A couple of weeks ago we noticed that whenever the door is closed, the carousel would spin continuously, and stop as soon as the door was opened. The interior light stays on as long as it’s plugged into the mains, the exhaust fan and oven surface light works normally. The clock display just indicates that the time needs to be set. The magnetron does not energize, it will not heat, and we have to leave it unplugged to prevent overworking the carousel motor. Does anyone have any ideas of what the problem could be?

Thanks!