How to Prevent Your Freezer from Building Up Frost

Freezers are supposed to be cold, but they’re not supposed to build up layers of fluffy frosty ice on the walls and everything stored in the freezer. If it’s starting to look like your freezer is getting freezer burn worse than a loosely packaged leftover, then something has gone wrong. It’s not that your freezer isn’t creating cold, it is. It’s that the defrost function inside your freezer isn’t functioning to ensure that everything stays perfectly frozen and frost-free. A freezer frosting over is more than just a space issue or the hassle of brushing icy moisture off your box of fish sticks. Ice building up over vent between the freezer and fridge can make the freezer too cold and the fridge not cold enough. Worse, ice built up over the evaporator can start to cause the freezer to warm up even though it’s covered in fluffy frost-ice. So how do you fix a freezer that won’t defrost? The answer could lie in one of three different options. It could be a defrost thermostat, the defrost timer, or the freezer door itself. We’ll look into each one to help you track down the source of your frost and how to get your freezer back to normal.  

Check the Door Sealing Gasket

The first and easiest thing to check is the condition of your freezer door. If the freezer door is not sealing correctly, then it could be letting in moisture from the outside of your normally very-dry freezer. This moist-er air freezes quickly inside the freezer compartment which can form an excessive amount of frost. So even if your defrost system were functioning perfectly, more frost would form than the system would be prepared to handle.

The key to your freezer sealing shut is the gasket, that rubber lining on the inside of the door itself. If the gasket is dirty, frosty, or damaged in some way then it will not form a perfect seal and moisture can seep in. Older gaskets may also have become small and hard due to a progressive lack of moisture.

If your gasket looks like it’s not damage, then wipe it clean and apply a thin layer of vaseline which can extend the life and functionality of the gasket. If the gasket is too old/hard or damaged, then replacing it is not a difficult repair. 

Test the Defrost Thermostat

Your defrost thermostat is what tells the freezer when to defrost and when to stop defrosting. When the freezer reaches a certain level of cold the defrost thermostat may trigger a defrost cycle. But more importantly in a timer-based defrost system, the thermostat lets the defrost system know when the freezer is getting too warm and to stop the defrost cycle.

However, if the defrost thermostat has stopped working, this can completely cut off your defrost system so that your freezer never goes through a defrost. So you’ll want to test your defrost thermostat if nothing was wrong with the door.

This is a real electrical repair-worthy process so you’ll need to temporarily unplug your freezer.

Locate the defrost thermostat behind the back panel or, in stacked-fridge models, sometimes underneath the freezer bottom panel. Detach the thermostat from any clips and from its own wires. Then hook up your multimeter to the thermostat’s own wires. If the thermostat is cold, then the reading should be zero. If the thermostat is warm, above 40 degrees F, then you should get a reading of infinity. If your test matches, reinstall the thermostat. Otherwise, install a new thermostat. 

Cycle the Defrost Timer

Finally, it could be your defrost timer. The defrost timer is often what determines when a defrost cycle starts, as opposed to the thermostat which typically ends a defrost cycle. The defrost timer is what triggers your freezer to regularly go through defrost cycles at a set interval so that ice never has a chance to build up on the walls and on your food items.

So if your defrost timer is busted, it would be no surprise that your freezer is never beginning the defrost cycles necessary to keep the frost at bay.

To test your defrost timer, you will also need to unplug your refrigerator for safety and remove an internal electrical part. Your defrost timer is located underneath the bottom kick-plate and has four metal prongs.

The prong connected to the white wire is your common terminal, remember this one as you fully remove the defrost timer from your fridge. You may have to use force or a rocking motion to loosen all the wires.

Test with your multi-meter by placing one probe on the common terminal (often labeled “C” or “3”) and then the other probe on each of the other three terminals in sequence. You should come out with a response of two prongs at zero (or near zero) and one prong at infinity. If so, return the defrost timer, it’s not the problem. If you get any other result, replace your defrost timer.

—If all three of these solutions have been tried, tested, and/or repaired and you’re still getting a frosty freezer, it’s time to call in the big guns. It’s very handy to be able to perform your own at-home repair diagnostics. Especially if you can quickly solve a home problem on your own. However, sometimes an issue needs the skill and insights of an experienced appliance repair technician.

It’s important to know when to call a technician to take over the diagnosis and repair process. If you’re not comfortable opening up your freezer and removing small electrical parts to test, that’s very normal and it’s quite alright to call a technician to take care of testing and replacement procedures for you. And if you love DIY but the problem is beyond you, it’s also okay to ask questions while your appliance repair technician inspects your freezer and hunts down the cause of your excessive frost problem. Whatever path you choose, stay safe when working with electrical parts and know when it’s time to call for backup.

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