Whirlpool WP4358609 Microwave Thermostat 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.

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.

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!