Frigidaire Range Error Code F7 21

F7 21 indicates that the left rear burner potentiometer has been detected in a shorted condition. The potentiometer is the variable resistor connected to your burner control knob, and it sends position signals to the User Interface Board. When the board reads an abnormal signal from this component, it sets the F7 21 fault code and may disable the affected burner.

You should avoid using the left rear burner while this fault is active, as the range cannot properly regulate that burner's output. Other burners not associated with the fault may still function, but operating the faulty burner without a working control signal creates an unpredictable and potentially unsafe condition.

If only the left rear potentiometer needs replacement, parts and labor costs are typically in the range of $75 to $175 depending on the specific model and local service rates. If the User Interface Board is also found to be faulty, costs can rise significantly, often falling in the range of $200 to $400 or more including parts and labor.

A knowledgeable DIYer with a multimeter can test the left rear potentiometer by checking for variable resistance through the knob's full range of motion. If the component reads zero or constant resistance, replacing the potentiometer is a feasible repair. However, if the potentiometer tests normally and the UIB may be at fault, professional diagnosis is recommended before purchasing a control board.

Disconnecting power to the range for a few minutes may temporarily clear the code, but it will return as soon as the control system re-detects the shorted potentiometer. A power reset does not address the underlying hardware fault, so the error will reappear during or after the next use of the left rear burner.