Frost buildup in freezer
Frost buildup in a freezer comes from warm, humid air getting in and freezing on cold surfaces. The usual culprits are a leaky door seal or a door that isn't closing all the way. On a frost-free freezer, a thick layer of frost on the back wall can also mean the automatic defrost system has stopped working. Find the source, defrost the freezer safely, and keep an eye on whether the frost comes back. Frost is just moisture that got in. Find where the warm air is sneaking in, and the frost stops.
Why frost builds up
Every time warm air reaches the inside of a freezer, the moisture in it freezes onto the coldest surfaces. A little is normal. A lot builds up when air keeps leaking in through a bad gasket, a door that's propped open by a crowded shelf, or constant opening in a humid kitchen.
Frost-free freezers fight this by running a heater on the evaporator coil a few times a day to melt the frost, which then runs down a drain to a pan under the fridge. If the heater, its timer or control, or its thermostat fails, frost builds up on the coil, often showing up as frost on the back panel and weak cooling. If the drain clogs, the meltwater refreezes as ice in the bottom of the freezer.
Common causes of freezer frost
Warm, moist air seeps in around the edges.
Food or a misaligned door leaves a small gap.
Meltwater refreezes in the bottom of the freezer.
The heater, timer, control or thermostat stops melting frost off the coil.
| You notice | Likely cause | Start at |
|---|---|---|
| Door bounces back open | Food blocking the door | Step 1 |
| Frost around the door edges | Leaky gasket | Step 2 |
| Gasket sticky or twisted | Gasket not sealing | Step 3 |
| Thick frost everywhere | Needs a full defrost | Step 4 |
| Sheet of ice on the freezer floor | Clogged defrost drain | Step 5 |
| Heavy frost on the back panel | Auto-defrost failure | Step 6 |
Let's fix it
- Check that the door closes fullyOpen the freezer and look for anything sticking out past the shelf edges, like a bag, ice tray or box, that could hold the door slightly open. Close the door gently and watch it seat. On many fridges, the front legs or leveling feet should be raised slightly so the door swings shut on its own.
- Test the door sealClose the door on a dollar bill so it's half in and half out, then pull it. You should feel some drag. Repeat around the whole door, including the hinge side and corners. If the bill slides out easily anywhere, the gasket isn't sealing there.
- Clean or reseat the gasketWash the gasket with warm soapy water and dry it, since sticky residue can keep it from sealing. If a section is twisted or flattened, warming it with a hair dryer on low for a short time can help it reshape; keep the dryer moving and away from the plastic liner. A gasket that's torn or still won't seal needs to be replaced with the part for your model.
- Defrost the freezerMove food into a cooler with ice packs and unplug the fridge. Leave the door open, lay towels on the floor and in the bottom of the freezer, and let the frost melt. A bowl of hot water set inside on a towel speeds it up. Don't use knives, ice picks or other sharp tools, which can puncture the refrigerant lines, and don't point a heat gun or hair dryer at plastic liners.
- Clear the defrost drainOn a frost-free freezer, look for a small drain hole at the bottom of the back panel or in the freezer floor. If ice has built up around it, melt it, then flush the drain with warm water using a turkey baster until it runs freely. On some models you need to remove the back panel to get to it, so check your manual. Once it's clear, dry everything, plug the fridge back in and wait until it's cold before reloading.
- Watch for frost coming backOver the next week, check the freezer every couple of days. Light frost near the door that keeps coming back points to the seal or a door that's opened often. Heavy frost on the back panel within a few days, especially with the fridge section getting warm, usually means the auto-defrost heater, its control or its thermostat has failed.
Watch it done
- No new frost after a week
- The door seals evenly on the dollar bill test
- Food stays frozen solid
If the frost comes back
If you've fixed the seal and the door closes well but frost still builds slowly, look at how often the freezer is opened and how humid the kitchen is. Some frost is normal on a manual-defrost freezer, which needs defrosting whenever the frost gets about a quarter inch thick.
If the frost comes back thick on the back panel and the fridge isn't cooling well, we have a guide for a fridge not cooling and call a technician to check the defrost system.
What a pro typically charges (a rough estimate; prices vary by area): An appliance repair visit usually runs $100–$200. Replacing a defrost heater or defrost thermostat typically costs $150–$350, a defrost timer or control board $150–$450, and a door gasket $100–$300 installed.
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Freezer frost questions
Why is there so much frost in my freezer?
Usually a leaky door seal or a door that isn't closing fully, letting humid air in.
How do I defrost a freezer quickly?
Unplug it, move the food to a cooler, and set a bowl of hot water inside with the door open.
Can I use a knife to remove ice from the freezer?
No. Sharp tools can puncture the refrigerant lines. Use a plastic scraper and let it melt.
Why does a frost-free freezer build up frost?
The auto-defrost heater, timer, control or thermostat may have failed, or the defrost drain is clogged.
Why is my freezer frosting up?
Warm, humid air is getting in and freezing, usually through a leaky door seal or a door that isn't closing all the way.