Refrigerator Knocking Noise: How to Diagnose and Fix

Quick answer

A refrigerator knocking noise often comes from the evaporator fan motor or defrost timer. Turn off the power, check for ice buildup, and inspect the fan blades and motor for damage or obstructions. Replace faulty parts if needed.

Confirm the symptom

• Knocking or thumping sound from the fridge
• Noise occurs when the compressor is running
• Sound may be rhythmic or irregular

Tools and prep

• Screwdrivers (flathead and Phillips)
• Flashlight
• Multimeter (for testing electrical components)
• Rubber mallet (optional)
• Safety gloves
• Turn off the refrigerator power before starting

Step-by-step troubleshooting

1. Inspect the Evaporator Fan Motor
   Do: Remove the back panel of the freezer compartment to access the evaporator fan.
   Observe: Check for ice buildup on the fan blades or motor.
   Means: Ice or a faulty motor can cause knocking.
   Next: Defrost the area if ice is present. If the fan is damaged, replace it.
2. Check the Condenser Fan
   Do: Locate the condenser fan at the back or bottom of the fridge.
   Observe: Look for obstructions or damaged blades.
   Means: A blocked or broken condenser fan can create noise.
   Next: Clear any debris. Replace the fan if necessary.
3. Test the Compressor
   Do: Use a multimeter to test the compressor's start relay and windings.
   Observe: Unusual resistance readings or no power to the compressor.
   Means: A failing compressor may cause knocking sounds.
   Next: Replace the compressor if faulty.
4. Examine the Defrost Timer
   Do: Access the defrost timer (usually near the compressor).
   Observe: Check for signs of wear or failure.
   Means: A faulty timer can prevent proper defrosting, leading to ice buildup and noise.
   Next: Replace the defrost timer if damaged.
5. Inspect the Leveling Legs
   Do: Check the refrigerator's leveling legs for looseness or damage.
   Observe: Uneven or wobbling legs.
   Means: Improper leveling can cause the fridge to knock.
   Next: Adjust or replace the leveling legs as needed.
6. Check the Door Hinges
   Do: Examine the door hinges for looseness or misalignment.
   Observe: Wobbly or noisy hinges when opening/closing the door.
   Means: Loose hinges can create knocking sounds.
   Next: Tighten or replace the hinges.
7. Look for Foreign Objects
   Do: Search inside the fridge and around the internal components for loose items.
   Observe: Any loose objects that could be vibrating or knocking.
   Means: Foreign objects can cause intermittent knocking.
   Next: Remove any found objects.

Common causes

Parts matching

Replace damaged or faulty parts with the correct refrigerator components:

• Evaporator Fan Motor – matches the model and size of your fridge
• Condenser Fan – compatible with your refrigerator’s make and model
• Defrost Timer – specific to your fridge’s system
• Leveling Legs – adjustable and durable for stability
• Door Hinges – matching the style and size of your refrigerator

Always refer to your refrigerator’s manual for the correct part numbers and specifications.

When to call a professional

• The knocking noise persists after checking all components
• You suspect a faulty compressor and lack the tools or experience to replace it
• The refrigerator is under warranty and you don’t want to risk voiding it
• You are unsure about electrical testing or component replacement
• The noise is accompanied by other issues like poor cooling or excessive vibration

FAQ

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