Display shows F4 and the refrigerator may not defrost properly, leading to frost buildup on the evaporator and poor cooling.

Safety warning: Disconnect power before removing the freezer rear panel. Edges of metal panels and coils can be sharp; wear cut-resistant gloves.

Diagnostic steps:

• 1. Empty and access evaporator: Remove freezer drawers/shelves. Unscrew and remove the rear interior panel to expose the evaporator coil.
• 2. Check for heavy frost: If the coil is encased in ice, defrost the unit completely (unplug, doors open, towels in place). Do not chip ice with sharp tools.
• 3. Locate the sensor: The evaporator sensor is usually clipped to the coil or attached to the refrigerant line. Ensure it is firmly attached and not hanging loose.
• 4. Test the sensor: With the fridge unplugged, disconnect the sensor connector and measure resistance. Compare to expected NTC values at the approximate coil temperature. Replace if readings are open, shorted, or far off spec.
• 5. Inspect wiring: Look for brittle or broken insulation from repeated freezing and thawing. Repair or replace damaged harness sections.
• 6. Control board check: If the sensor and wiring are good, the main control board may not be processing the signal correctly and may require replacement.

After repair: Reassemble panels, restore power, and allow 24 hours for normal frost pattern and temperatures to return.