Whirlpool Refrigerator will not defrost

Hi @gwhitten,

Besides the temperature control thermister, usually there's also a defrost thermistor¹ that is used to cut off the defrost heater if the temperature rises above a pre-set upper limit.

It may be that this thermistor is faulty.

Testing the defrost heater function using the diagnostics may be inconclusive because the diagnostics just check if it works or not, not how it operates during normal defrost operation, so perhaps the defrost temp sensor resistance value indicating the temperature of the evaporator unit is not taken into account.

Not sure if there's a diagnostic test for the defrost thermistor to check if this is the case or even to test if it is OK or not as I cannot find a download for the tech sheet (p/n W11212322) for the refrigerator online.

Check if there's a tech sheet located as shown in the image below

(click on image)

¹ That is if there is a separate defrost sensor. They may just use the thermistor that is already in the freezer (clipped to the evaporator unit?) and use it to indicate the temp during the defrost cycle as well as the normal freezer temperature.