Whirlpool Washer Error Code F40

F 40 means the washer's ATC (Automatic Temperature Control) thermistor has been detected as open or shorted. This thermistor is responsible for measuring incoming water temperature so the machine can blend hot and cold water correctly. When the control board receives a signal outside the expected resistance range, it triggers this fault code and stops the cycle.

You should not continue running the washer with an active F 40 code. Without accurate temperature sensing, the ATC system cannot properly regulate water temperature, which could result in water that is too hot or too cold for your laundry. Most machines will halt the cycle automatically when this fault is present.

Resetting the washer may temporarily clear the F 40 code, but it will return if the underlying fault is not repaired. A reset does not fix a failed thermistor, damaged wiring, or a faulty control board. Proper diagnosis using the TEST #5 procedure is necessary to identify and correct the root cause before the washer will operate reliably.

A knowledgeable DIYer can often diagnose and fix this error by testing the thermistor and wiring harness with a multimeter as outlined in the washer's TEST #5 procedure. If the thermistor has failed, replacing it is a relatively straightforward repair. However, if the control board is the root cause, professional service is recommended due to the complexity and cost of that repair.

If only the ATC thermistor needs replacement, parts and labor typically cost in the range of $75 to $200 depending on your location and service provider. If the wiring harness requires repair, costs are similar. A control board replacement is significantly more expensive, often ranging from $200 to $400 or more for parts and labor combined.