Display shows dH and refrigerator may show warm temperatures or excessive frost in freezer.

Safety first: Unplug the refrigerator immediately if you suspect a heater stuck on, as this can be a fire risk.

• Inspect evaporator area: Remove the freezer rear panel and check for signs of overheating, melted plastic, or strong burnt odor near the defrost heater.
• Test defrost thermostat: With the evaporator warmed to room temperature, the defrost thermostat should be open (no continuity). If it remains closed, replace it.
• Check heater resistance: Disconnect heater leads and measure resistance. A shorted heater may show abnormally low resistance or visible damage.
• Thermistor check: Ensure the evaporator thermistor is properly clipped to the coil and not damaged. Replace if corroded or reading out of spec.
• Control board evaluation: If the heater and thermostat are normal, the main control board may be keeping the heater energized too long. Replacement of the board is typically required and is best done by a professional.