Greg K Park City , UT January 20, 2020 Appliance: Whirlpool Microwave WMH73521CS0 Whirlpool Microwave Wmh73521cs0: Microwave would not turn on it sensed the door was always open. How to replace Microwave Door Interlock Switch. We replaced all 3 switches in the upper and lower latch assembly. There were 2 in the upper and 1 in the lower. I know that seems odd, but it was true for our unit. 1 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: 30-60 minutes