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Why Your Fridge Is Not Defrosting – Common Causes & Easy Fixes

freezer not defrosting evaporator has ice buildup

Troubleshooting Guide • Updated Sep 8, 2025

Fridge Not Defrosting? Causes, DIY Checks, and When to Call a Pro

From the technicians at Advance Appliance Ltd serving Edmonton, Calgary, and Red Deer.

Quick signs your fridge isn’t defrosting

  • Freezer back wall is packed with snow-like frost.
  • Freezer stays cold, but fresh-food section turns warm.
  • Fan noise grows louder or stops (ice blocking airflow).
  • Water under crispers after a partial thaw/refreeze.
  • Error codes related to defrost or sensors (on some models).

Why it matters

Without defrost, the evaporator coils ice up, choking airflow. Food temps rise, compressors overwork, and energy bills climb. A prompt fix protects food safety and the appliance.

Top causes (and what they mean)

1) Defrost heater failure

The heater can’t melt frost, so ice steadily builds. Often shows as a full snow blanket over the evaporator.

2) Defrost thermostat / bimetal

If stuck open, the heater never energizes. If stuck closed, it can overheat and trip safeguards.

3) Control board or defrost timer

Newer models use boards; older ones use timers. If schedules don’t trigger, frost wins.

4) Thermistor / defrost sensor

Bad readings confuse the board. Result: sporadic or zero defrost cycles.

5) Wiring & connectors

Heat and moisture can oxidize or burn terminals—no power to the heater.

6) Door gaskets

Leaky seals pull in humid air, growing frost faster than the system can melt it.

Tech tip: If you recently replaced a board or sensor and re-icing is fast, recheck connectors, harness routing, and sensor placement on the coil.

DIY checks (safe and simple)

  1. Unplug first. Remove the freezer rear panel to view the evaporator.
  2. Inspect frost pattern. Even, snow-like frost = defrost fault; thick ice block on one corner may be a sealed system issue (call a pro).
  3. Forced defrost test. Many models allow a service mode to activate the heater. Listen for faint sizzle; avoid touching live parts.
  4. Test the heater. With a multimeter, disconnect leads and check for continuity.
  5. Test the defrost thermostat/thermistor. Cold-closed thermostats should read continuity; thermistor ohms should match the brand chart.
  6. Check door gaskets. Look for tears, warping, or gaps. Close a paper strip in the door; if it slides out easily, the seal is weak.

Symptoms → Likely causes → Actions

Symptom Likely Cause What to Do
Freezer wall covered in snow-like frost Defrost heater failure; stuck-open thermostat; timer/board not initiating Forced-defrost test; test heater continuity; test thermostat/thermistor; inspect control/timer
Fresh-food warm, freezer OK Airflow blocked by ice on evaporator Defrost system diagnosis; avoid propping doors open long-term
Re-icing quickly after manual defrost Sensor misreadings; wiring/connector issues; door gasket leaks Verify thermistor values, connector integrity, and gasket seal tension
Breaker trips or burnt smell Shorted heater or damaged wiring Unplug immediately and book service

When to call a professional

Call a certified technician if breakers trip, there’s a burning smell, error codes persist, or ice returns quickly after a manual defrost. For fast, local help, book trusted refrigerator repair with Advance Appliance Ltd.

Service areas: Edmonton, St. Albert, Sherwood Park, Leduc, Spruce Grove, Calgary & area (Airdrie, Cochrane, Chestermere, Okotoks), and Red Deer & nearby communities.

FAQs

How long should a defrost cycle last?

Typically 10–30 minutes, model dependent. Some boards adapt timing based on door openings and compressor run-time.

Will unplugging overnight fix it?

It can temporarily restore airflow by melting ice, but the root cause (heater/thermostat/board) still needs diagnosis.

Is a hair dryer safe to melt ice?

No. It risks electric shock and component damage. Use time and ambient air only, or hire a professional.

© 2025 Advance Appliance Ltd • Edmonton | Calgary | Red Deer

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