There once was a young man whose very first apartment had an old freezer-on-top refrigerator that required manual defrosting from time-to-time. Not being familiar with how to accomplish this and having numerous distractions to keep his mind off this condition, the young man decided to ignore the issue. After about a couple of years, the ice build-up nearly filled the entirety from the freezer compartment, leaving only a small opening in the middle. This did not cause much consternation for the young man since he could still store up to two frozen TV dinners at any given time in that small opening (his main supply of sustenance).
The moral of this story? Progress is an excellent thing since nearly all modern refrigerators have automatic defrost systems to make sure your freezer compartment never becomes a solid block of ice. Alas, even defrost systems on the highest-end refrigerator models can malfunction, therefore it is a good idea to be familiar with how the system is supposed to work and how to repair it if it fails.
How an automatic defrost system works
As part of the refrigeration system to keep the refrigerator compartment a consistently cool temperature of around 40° Fahrenheit (4° Celsius) and the freezer compartment a chillier temperature near 0° Fahrenheit (-18° Celsius), the compressor pumps refrigerant in liquid form in to the appliance's evaporator coils (usually located behind a rear panel within the freezer compartment). Once the liquid refrigerant enters the evaporator coils, it expands right into a gas which makes the coils cold. An evaporator fan motor draws air within the cold evaporator coils then circulates that air with the refrigerator and freezer compartments.
The evaporator coils will collect frost because the air drawn by the fan motor passes them over. Without periodic defrosting, frost or ice can build-up on the coils which can significantly impact air flow and prevent the refrigerator from cooling properly. This is when the appliance's automatic defrost system comes into play. The basic components in this system include a defrost heater, a defrost thermostat, along with a defrost control. Depending on the model, the control can be a defrost timer or a defrost control board. A defrost timer turns the heater on for a duration of about 25 minutes 2 or 3 times a day to prevent the evaporator coils from frosting over. A defrost control board will also turn the heater on but will regulate it more efficiently. The defrost thermostat plays its part by monitoring the temperature of the coils; when the temperature drops to some set level, the contacts in the thermostat close and allow voltage to power the heater.
Five causes of why your defrost system is not working
If the evaporator coils show indications of significant frost or ice build-up, the automated defrost system is probably malfunctioning. Listed here are the five more likely reasons why:
- Burned out defrost heater – When the defrost heater is unable to “heat up”, it will not be much good at defrosting. You can often tell that a heater has burned out by checking to see if there is a visible break in the component or any blistering. You may also use a multimeter to test the heater for “continuity” – a continuous electrical path present in the part. If the heater tests negative for continuity, the component is certainly defective.
- Malfunctioning defrost thermostat – Since the defrost thermostat determines when the heater will receive voltage, a malfunctioning thermostat can avoid the heater from turning on. As with the heater, you can use a multimeter to check the thermostat for electrical continuity, however, you will need to do that at a temperature of 15° Fahrenheit or lower for a proper reading.
- Faulty defrost timer – On models with a defrost timer, the timer could neglect to advance into the defrost cycle or be able to send voltage to the heater during the cycle. Try slowly advancing the timer dial into the defrost cycle. The compressor should turn off and the heater should switch on. If the timer does not allow voltage to reach the heater or the timer doesn't advance out of the defrost cycle within 30 minutes, the component should be substituted for a new one.
- Defective defrost control board – If your refrigerator uses a defrost control board to control the defrost cycle rather than a timer, the board could be defective. While the control board can't be easily tested, you can inspect it for indications of burning or a shorted out component.
- Failed main control board – Since the refrigerator's main control board regulates the ability supply to all of the appliance's components, a failing board might be unable to allow voltage to become sent to the defrost system. Before you decide to replace a main control board, you need to rule out the other possible causes.
Keep your refrigerator defrosting with parts from Repair Clinic
Once you've determined that it's a defective heater, thermostat, timer, or control board that has caused your refrigerator's defrost system to fail, you'll need to find the specific part that matches your model. That's where Repair Clinic can help. Enter the full model number of the refrigerator in the Repair Clinic website search bar for an entire list of compatible parts. Make use of the “Part Category” filter (“Heating Element”) and “Part Title” filter (“Defrost Heater Assembly”) to narrow the list down to ID the exact part that fits your fridge. While Repair Clinic stocks parts for all the top brands in refrigeration, including Whirlpool, GE, Kenmore, LG, Samsung, Frigidaire, and Amana, entering the full model number of your refrigerator will make sure you find the right matching part.
