KitchenAid Refrigerator — Not Defrosting / Ice Buildup

About the Issue

If your KitchenAid refrigerator keeps building heavy frost or a solid ice block on the evaporator or back wall, the automatic defrost system is not keeping up. As ice grows, it blocks airflow, makes the fan noisy, and eventually causes warm fridge temperatures, longer run time, and poor performance.

On many KitchenAid French-door and side-by-side models, the control board energizes a defrost heater on a schedule, using data from thermistors and defrost thermostats. When one or more of these parts fail, frost never fully clears, so each cooling cycle adds more ice until the coil is packed and air can’t move through it.

Symptoms (What You May Notice)

• Thick frost or solid ice behind or around the rear freezer panel.
• Fan noise changes — buzzing, scraping, or intermittent squealing.
• Freezer may still feel cold, but the fridge section warms up.
• Visible frost around air vents, duct openings, or door rails.
• Water on the bottom of the freezer or ice under drawers after partial melts.
• Unit runs for long periods with shorter off cycles than before.

Causes (KitchenAid-Specific Patterns)

• Failed defrost heater that never melts ice from the evaporator coil.
• Defrost thermostat or bimetal not closing to allow heater operation.
• Control board or timer issues not initiating defrost cycles on schedule.
• Faulty thermistors sending wrong temperature data to the control.
• Drain clogs causing refreeze and ice buildup around the drain trough.
• Door gasket leaks or frequent door openings adding moisture and speeding frost.
• Incorrect previous “repairs” such as bypassed sensors or mismatched parts.

Tests (How We Pinpoint the Fault)

• Inspect the frost pattern on the evaporator coil and surrounding areas.
• Ohm and test the defrost heater for continuity and proper resistance.
• Check the defrost thermostat/bimetal for correct open/close behavior by temperature.
• Verify control board outputs to the heater and fan during test modes or cycles.
• Measure thermistor values and compare them with KitchenAid temperature charts.
• Inspect and clear the drain tube and trough for ice plugs or debris.
• Evaluate door gaskets, alignment, and closure to reduce excess moisture load.

These steps separate a simple drain or door issue from a true defrost system failure. We confirm the exact part causing the ice buildup before recommending replacement so that the refrigerator can return to normal automatic defrost.

Repairs (What We Do to Fix It)

• Safely de-ice the evaporator coil and fan area without damaging components.
• Replace failed defrost heaters, thermostats, or sensors as needed.
• Correct control board or timing issues that prevent defrost from running.
• Clear and treat drain clogs to prevent recurring ice at the bottom of the freezer.
• Adjust doors and restore gasket seal to reduce moisture entering the cabinet.
• Confirm proper defrost operation in test mode and during normal cycling.

Before finishing, we verify that airflow is restored, frost pattern is normal, and both freezer and fridge sections return to stable, food-safe temperatures without rapid ice buildup.

Prevention (Reduce Future Ice Buildup)

• Keep door gaskets clean and inspect them for tears, gaps, or hard spots.
• Avoid leaving doors open for long periods during loading or cleaning.
• Do not pack food tightly against the back wall or air vents.
• Address early signs of frost, water on the floor, or fan noise before the coil is fully iced.
• Schedule service if you find yourself manually defrosting the unit more than once — that’s a sign the automatic defrost system needs attention.