Whirlpool Cooktop Error Code F-21

F-21 on a Whirlpool cooktop indicates a supply power frequency error detected by the power control board. The board monitors incoming AC line frequency and flags this code when the frequency reading falls outside the acceptable range. All burners controlled by that board are disabled when F-21 is active. The power control board must be replaced to resolve the fault.

A power reset may temporarily clear the display, but F-21 will return if the power control board's frequency detection circuitry is genuinely faulty. Because the fault originates from within the board itself, resetting the appliance does not correct the underlying hardware failure. Board replacement is the only lasting fix.

Repair costs depend on the specific power control board part price and whether you hire a technician. Parts alone typically range from around $80 to $250 or more depending on the cooktop model. Adding professional labor, total repair costs often fall between $150 and $400. Getting a parts quote for your specific model before committing to the repair is recommended.

The repair requires disconnecting power to the cooktop and replacing the power control board. A knowledgeable DIYer comfortable working with appliance electronics can perform this repair, but working near line-voltage components carries real risk if proper precautions are not taken. If you are not confident working with high-voltage appliance components, hiring a qualified appliance technician is the safer choice.

No. When F-21 is active, the power control board disables the burners it controls, so the cooktop will not operate normally. You should not attempt to bypass this fault or continue using the appliance until the board has been replaced and the error is cleared.