Whirlpool Microwave Error Code F3.T4

F3.T4 indicates a magnetron thermistor failure. The magnetron thermistor is a temperature sensor mounted near the magnetron tube that monitors operating heat levels and sends signals to the control board. When the control board detects an abnormal or absent signal from this sensor, it displays F3.T4 and stops microwave operation to prevent damage from undetected overheating.

No, you should not use the microwave while F3.T4 is active. The magnetron thermistor is a safety component that protects against overheating. Operating the microwave without a functioning thermistor removes that thermal protection and could result in damage to the magnetron or, in a worst-case scenario, a fire or other safety hazard.

If only the magnetron thermistor needs replacement, the repair is generally affordable, with parts typically ranging from around $15 to $50 depending on the specific model. If professional labor is involved, total repair costs could range from $75 to $200 or more. If the control board is also at fault, costs will be higher, which may make repair less economical for older units.

A knowledgeable DIYer can address this fault by first unplugging the microwave and checking the thermistor's wiring connector for looseness or corrosion. If the connection is secure, the thermistor can be tested with a multimeter and replaced if faulty. However, it is critical to ensure the microwave is fully unplugged and that the high-voltage capacitor is discharged before working near the magnetron area, as serious electrical hazards exist even with the unit powered off.

Unplugging the microwave and restoring power may temporarily clear the fault display, but if the thermistor or its wiring is defective, the F3.T4 code will return as soon as the microwave attempts to operate again. A reset does not repair the underlying hardware fault. The thermistor connection and component condition must be properly diagnosed and addressed.