Whirlpool WP4358609 Thrmst - Fix OEM Part

Replaced a bad thermostat. The factory thermostat had a bad internal connection (one contact was loose) and that caused the insulation to melt with the eventual failure of the thermostat. I ordered the exact replacement part from "AppliancePartsPros.com" and quickly saved the cost of a new built in Microwave oven.

First checked the breaker at the electrical panel and it wasn't tripped. I then unplugged and opened the microwave to check the fuse for continuity and it was fine. Next I checked the cavity thermistor and it was open. Upon further investigation I noticed the cavity thermistor was slightly deformed as well. After ensuring the internal capacitor was fully discharged, I check the rest of the microwave over for possible additional component failures. Everything else was found to be satisfactory, so I found the correct replacement cavity thermistor part on AppliancePartsPros.com and placed my order. After receiving the new cavity thermistor I checked the continuity to ensure it was operational then I installed it into my microwave and tested the microwave's operation. As soon as I plugged it in I noticed the display was functioning again. Then I placed a cup of water in the microwave to further test it's operation. The microwave is back up and running! Although I am trained in electronics I found the following YouTube video very helpful: https://www.youtube.com/watch?v=t1tdj3OnlXU Good Luck!

I unplugged the device, opened the case, shorted the capacitor's terminals together with a screwdriver (safety precaution--always do this with a microwave oven--the stored power in the capacitor can pack a wallop if you don't discharge it first), and just looked around. I quickly saw that the wiring to one terminal of the thermostat was black and melted. Nothing else looked amiss, so I figured this was the problem. (I also figured out how to read the wiring diagram and confirm the problem with my ohm meter, but even if I couldn't have done that, I was already convinced that the burned thermostat was almost certainly the problem.) Ordered a new thermostat and installed it when it came. I had to cut off the burned connector and crimp on a new one I got at the local hardware store. Wrapped the new terminal+connector in electrical tape for insulation. Put the cover back on, tested the microwave, and all was well. Took about 30 minutes total.