The defrost thermostat monitors the temperature of the evaporator coils. When the coils become too cold, the thermostat closes to allow electricity to flow to the defrost heater. This occurs during the defrost cycle when the heater melts frost accumulating on the coils. If the thermostat is faulty, the contacts won't close to power the heater. To check if the thermostat is defective, use a multimeter to test for continuity. If there is no continuity when the thermostat reaches its low operating temperature, replace it.
The defrost control board regulates when the defrost cycle runs. If the board malfunctions, the freezer will not initiate the defrost cycle. Prior to replacing the defrost control board, first examine the defrost heater and defrost thermostat. If the heater and thermostat are functioning correctly, the defrost control board is likely faulty. Replacing a defective defrost control board allows the freezer to go through the regular defrost cycle again to prevent frost build up on the evaporator coils.
The main control board controls electricity to all freezer parts, including the defrost system. If the main board malfunctions, it may stop powering the defrost system. Control boards are often misdiagnosed. Prior to replacing the main board, first test all defrost system components. If none of the defrost parts are faulty, consider replacing the main control board. Testing the defrost heater, thermostat, timer, and other components first prevents unneeded replacement of the main board. Only replace the main control board if other defrost system parts are confirmed to be working properly.
If the door gasket does not seal properly, ice can accumulate where air leaks through. Inspect the gasket for any kinks or twists. Try smoothing kinks using a hair dryer's heat. If the gasket is damaged or worn out, replacement is required. Check for cracks, brittleness, or detachment from the door frame. Test the seal by closing a piece of paper in the door and tugging - it should not pull out easily. Apply a thin layer of petroleum jelly to the gasket every few months to maintain flexibility. Replacing a worn or damaged gasket improves the seal and prevents cold air loss and frost buildup from air leaks.
In self-defrosting freezers, the defrost heater system activates periodically to melt frost building up on the evaporator coils. If the defrost heater is faulty, the defrost mechanism will fail, allowing frost to continue accumulating on the coils. To check if the defrost heater is defective, use a multimeter to test for continuity. If there is no continuity, the defrost heater needs replacement. Replacing a defective defrost heater enables the self-defrosting system to properly melt away frost so it does not reduce the freezer's efficiency.
In some models, the user control and display board also regulates the defrost system. These boards are often misdiagnosed. Prior to replacing the user control board, first examine all defrost system parts. If none of the defrost components are faulty, consider replacing the user control and display board. Testing the defrost heater, thermostat, timer, and other components first prevents unneeded replacement of the user control board. Only replace the user control and display board if other defrost system parts are confirmed to be working properly.
The defrost timer activates the defrost heater periodically to melt frost on the evaporator coils. If faulty, the timer may not start the defrost cycle or power the heater during it. To check if the timer is defective, slowly turn the dial into the defrost cycle. The compressor should stop and the heater should activate. If the timer does not send electricity to the defrost parts or end the defrost cycle within 30 minutes, it is likely defective and requires replacement. This allows the timer to turn on the defrost heater regularly to clear frost accumulation so the freezer can function efficiently.
Chest freezers and certain upright freezers with evaporator tubing in the shelves require manual defrosting. This means disconnecting power to the freezer for a period to melt built-up frost and ice. If the accumulation reaches 1/4 to 1/2 inch thick, defrosting is needed. To defrost, unplug the freezer and remove any food items. Keep the door open as the ice melts to allow water to drain out. Use towels to soak up excess water. Avoid using sharp tools to scrape ice as they can damage the freezer interior. Once fully defrosted, clean and dry the interior before turning the freezer back on. Performing periodic manual defrosting maintains freezer efficiency.
Excessive frost buildup on food and around the door opening typically indicates the door was left open or ajar for an extended time. Frequent frost accumulation can reduce freezer efficiency and force more frequent defrosting. To prevent excessive frost, make sure the door is completely closed after each use. Check that the door gasket seals properly all the way around. Replace the gasket if it is cracked or damaged. Organize food containers to prevent blocking the door. Listen for the door latch clicking when closed. Take note of any objects obstructing full door closure.