Refrigerator Defrost problems – Diagnosing the most common malfunction of refrigerators and freezers

Oct 13, 20 • DIY TipsNo Comments

All Brands (Whirlpool, GE, Frigidaire, Electrolux, LG, Samsung, Kitchenaid, etc..) of Frost-Free Refrigerators and Freezers Have Defrost Systems.

Symptoms:

  1. Food in the freezer is soft and cold drinks in the refrigerator are no longer as cold as they have been. 
  2. Adjusting temperature settings does not result in colder temperatures.   

 

Confirming your refrigerator has a defrost system malfunction.

  1. The Defrost problem can be confirmed by removing food from the freezer.
  2. Remove the freezer interior panels that cover the cooling coils.  
  3. A defrost problem is confirmed if the cooling coils are covered with ice.  If there is no ice then the defrost system is working normally and you must look elsewhere for the source of your refrigerator malfunction.  Call U-FIX-IT Appliance Parts for free diagnosis assistance.
    • Ice acts as an insulator preventing the cooling coil from lowering the temperature in the freezer compartment to the desired setting.
  4. A hairdryer can be used to defrost the ice. Ice picks are a bad idea.
    • The freezer (and refrigerator) will operate normally after the ice is removed.
    • Normal operation will continue until the coils are again covered in ice which is usually about three days.  Food can be protected by continuing to defrost manually as needed until the repair is made.

 

Three components of the defrost system.

  1. Defrost Heater
  2. Defrost termination switch (thermostat).
  3. Defrost timer or control board.

 

Purpose of Defrost System

The refrigerator and freezer doors will be opened and closed numerous times as family members store and retrieve food and drink. Every opening and closing of the doors allows air from the room to enter.  Cold surfaces inside the freezer will cause moisture in the air to condense and form frost on the food items and cooling coils. Over time frost that is not removed will build up eventually forming solid ice. The defrost system prevents the buildup of frost and ice by periodically initiating the defrost cycle.  

 

Defrost System Operation

  1. The defrost timer or control board initiates the defrost cycle. 
    • Mechanical timers initiate and terminate the cycle based on time.
    • Control boards initiate and terminate the cycle utilizing combinations of time, logic, and temperature sensing.
    • Timers and control boards are commonly located in the refrigerator section near the temperature controls behind plastic panels.  Control boards may be mounted on the back of the refrigerator.  Call U-FIX-IT Appliance Parts with your model number if you need help locating your board. 
  2. The defrost cycle blocks power to the compressor and sends power to the defrost heater.
    • Heaters are usually calrod heaters (look like small bake elements) or elements encased in a glass tube.
    • Heaters will be fastened to the bottom of the cooling coils in the freezer section.  High-end refrigerators with cooling coils in the refrigerator section will have a second defrost heater.  Most refrigerators have one heater.
    • The heat from the heater will melt the frost and ice on the cooling coil.  The water (melted ice) runs down the cooling coils into a trough below the coils.  Water collected in the trough is routed to a condensate pan located in the compressor section where it evaporates back out into the room from whence it came.
  3. The defrost termination switch (thermostat) or in some cases, a temperature sensor stops the heater from thawing the food in the freezer during the defrost cycle.
    • Power is routed through the defrost termination switch (thermostat) to the heater.
    • The defrost termination switch (thermostat) is mounted to the coil at the top.  
    • The defrost termination switch (thermostat) will cycle power to the heater off and on for the duration of the defrost cycle.
      • As the heater raises the temperature of the defrost termination switch (thermostat) the power will cycle off to the heater.
      • As the temperature of the defrost termination switch (thermostat) cools the power will be restored to the heater.
    • Some defrost systems use a temperature sensor instead of the defrost termination switch (thermostat).
      •  Temperature sensors and heaters connect directly to the control board.
      • Power to the heater is controlled by the control board.

 

The Quick Solution:

Repair technicians will usually replace all three components of the defrost system whenever it malfunctions.  The symptoms are the same no matter which one of the three components fails and all three are the same age.  Replacing all three eliminates the need to isolate which one of the three is bad.

Identifying Which One of the Three Defrost Components is Bad:

  1. Defrost heater is good if it has continuity between the leads and no continuity to ground. 
  2. The defrost termination switch (thermostat) is good if it has continuity when cooled below 40 degrees.
    • Temperature sensors can be tested by reading the resistance (ohms) at room temperature.  Call U-FIX-IT with your model number for the ohm reading for your sensor.
  3. If the defrost heater and termination switch (thermostat) test “good” then the defrost control (timer or board) needs to be replaced. 
  4. U-FIX-IT will test the heater and thermostat free of charge if you remove them and take them (along with a cup of ice) to your nearest U-FIX-IT Appliance Parts store.

 

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