Compressor

• As the metal parts within the refrigerator expand and contract when the compressor turns on and off, a popping, cracking or knocking sound may result. This sound generally should be pretty quiet, shouldn’t last long and is most likely in older model refrigerators. The knocking is not necessarily a problem unless the sound is very loud, lasts for a long time or there are other issues, such as poor cooling. If these conditions exist, contact Kenmore for service assistance.
  
  

Vibration

• Luckily for some owners, the knocking problem may not come from the compressor or other refrigerator components at all. Instead, the refrigerator may simply be in contact with a wall and is making sound when the refrigerator vibrates during normal use. This knocking sound can be resolved by allowing a space of 2 to 4 inches between the refrigerator and any other surface.
  
  

Condenser

• The condenser, which is partially responsible for cooling in the refrigerator, frequently gets covered in dust or dirt and starts to lose effectiveness. When this happens, the refrigerator or freezer may not be as cold and there may be a knocking sound due to reduced air flow over the condenser. Clean the condenser yourself by disconnecting power to the Kenmore refrigerator and using a soft brush or vacuum brush attachment to clean off the condenser, which looks like a bunch of black coils in the rear of the refrigerator.
  
  

Condenser Fan

• Along with the condenser, the condenser fan also helps cool the refrigerator and can start to make noise if dirty or obstructed. When you are cleaning the condenser, use the brush or vacuum brush attachment to clean the condenser fan as well. Sometimes there is a thin cover over the fan in the back of the refrigerator that you will need to remove with a screwdriver first.