Saturday night, I went to heat up some food in my Whirlpool microwave.
I punched in the time and hit start. The interior light came on but
nothing else happened. I removed the cover and noticed the document
entitled "Tech sheet - Retain for service technician only" packed in a
little envelope under on top of the oven.
Looking at the schematic, I noticed the symptoms pointed to a failed
primary interlock switch. I located the switch right behind the door
latch. It's one of three safety switches on this unit. Sure enough, the
switch clicked just like a good one but no continuity. A trip to my
local electronics store and $4 later, I had the switch in and the oven
was once again producing hot food!
Of note: This is a SPDT miniature microswitch with a button actuator
and a 15 amp at 250 Volt rating.
Just posted this so that it might help someone else.