Refrigerator displays dF or remains in defrost mode too long; temperatures may rise during extended defrost.

Safety first: Disconnect power before accessing the evaporator area or testing the defrost circuit.

Step 1: Inspect evaporator frost pattern

• Remove freezer baskets and the rear evaporator cover.
• If the evaporator is completely encased in ice, the defrost system is likely not working.

Step 2: Test the defrost thermostat (bi-metal)

• Locate the defrost thermostat clipped to the evaporator tubing.
• With the evaporator still cold (below freezing), disconnect the thermostat and test for continuity with a multimeter.
• If it is open when cold, the thermostat is defective and should be replaced.

Step 3: Test the defrost heater

• Disconnect the heater leads and measure resistance. A typical heater will show a finite resistance (often 20–100 ohms depending on design).
• If the heater is open (OL), replace it.

Step 4: Check defrost sensor/thermistor

• Some Frigidaire Gallery models use a thermistor for defrost control. Test resistance against the tech sheet chart.
• Replace if readings are out of range.

Step 5: Control board evaluation

• If heater and thermostat/sensor test good, the main control board may not be initiating defrost properly and may need replacement.

When to call a technician: If you are not comfortable testing live circuits or replacing heaters, contact a professional.