Frost Building Up in the Freezer: Causes and How to Fix It
Frost on food and freezer walls usually comes from warm, humid air getting in through a bad door seal or a door left ajar. Frost on the back panel or a warm fridge points to a failed defrost system.
- Difficulty
- Easy
- Time
- 30 minutes to check; a day to defrost manually
- Typical cost
- $0 for checks; a door gasket or defrost part costs more
Frost forms when moisture in the air freezes on cold surfaces. A little frost is normal in a manual-defrost chest or upright freezer. In a frost-free refrigerator-freezer, though, visible frost on food packages, walls or shelves means more moisture is getting in, or less is being removed, than the design allows. Finding which tells you whether the fix is a seal, a habit or a repair.
Diagnose the frost
| Where the frost is | Likely cause |
|---|---|
| Near the door edge or one corner | Door seal leaking at that spot |
| On food packages and walls throughout | Door left ajar, frequent opening, warm food added, high room humidity |
| Thick frost behind the back panel or on the evaporator cover | Defrost system failure |
| Frost plus a warm fresh-food section | Evaporator iced over, blocking airflow |
| Frost on ice cubes and ice maker | Normal over time; empty and refill the bin |
| Manual-defrost freezer | Normal; defrost periodically |
Step 1: Test the door seal
ENERGY STAR recommends checking that door seals are airtight and replacing them if not, and keeping the door closed as much as possible. To test, close the door on a strip of paper at several points around the seal. If it pulls out with little resistance, the seal is weak there. Clean the gasket with warm soapy water; dried spills can keep it from sealing. A gasket that is torn, flattened or stiff should be replaced with the part for your model.
Step 2: Make sure the door closes
- Check that food packages, bins or the ice bin are not keeping the door slightly open.
- Level the refrigerator so it tilts slightly back and doors swing closed on their own, as described in your manual.
- Check that the door is not sagging; loose hinges can break the seal at the top or bottom.
Step 3: Change habits that add moisture
- Let hot food cool before freezing, and package it in airtight containers or freezer bags.
- Avoid holding the door open while deciding what to take.
- In humid summers or a hot garage, freezers work harder and frost more; ENERGY STAR advises placing refrigerators away from heat sources such as ovens and direct sunlight.
Step 4: Defrost manually
If frost is heavy, a manual defrost clears it so you can see whether it returns:
- Move food to a cooler with ice packs. USDA’s refrigeration guidance includes food safety steps for keeping food cold while defrosting.
- Unplug the refrigerator and leave the doors open.
- Place towels and shallow pans to catch water.
- Let frost melt on its own, or speed it with bowls of hot water placed inside. Do not use sharp or metal tools; scraping can puncture refrigerant tubing.
- Dry the interior, plug the unit in and let it reach temperature before restocking.
Step 5: Watch for defrost failure
Frost-free refrigerators melt frost off the evaporator coil automatically several times a day using a defrost heater controlled by a timer or control board and a defrost thermostat. If thick frost returns behind the back panel within days of a manual defrost, one of those parts has likely failed. A common sign is a freezer that stays cold while the fresh-food section warms up, because frost blocks the airflow that cools it.
Manual-defrost and chest freezers
Chest freezers and many compact uprights have no automatic defrost, so frost buildup is expected. Plan to defrost them when frost reaches the thickness your manual recommends, since thick frost insulates the walls and makes the freezer work harder. Defrosting during cold weather, or when the freezer is nearly empty, makes keeping food frozen in a cooler easier. Dry the interior completely before switching it back on so new frost does not form immediately.
Common mistakes
- Chipping ice with a knife or screwdriver.
- Using a heat gun on plastic liners.
- Ignoring a torn gasket, which wastes energy as well as causing frost.
- Overpacking the freezer so the door cannot close.
When to call a technician
Call an appliance technician if frost keeps returning behind the back panel, if the fresh-food section warms while the freezer is cold, if the drain at the bottom of the freezer keeps freezing, or if the door gasket is not owner-replaceable on your model. Defrost heater, thermostat and control repairs require accessing parts inside the freezer and testing electrical components.