Why Is My Dehumidifier Freezing Up? The Reasons and the Fix

A frozen dehumidifier is not something you want to ignore. Not only do frozen coils mean the unit can’t pull humidity from the air effectively, but they can also cause irreparable damage to the appliance.

If your dehumidifier is icing up, it’s important to identify the reason so you can fix it as soon as possible.

So, why do dehumidifiers freeze up? The most common reason dehumidifiers freeze up is because the room temperature is below 65 degrees. But other causes, like poor airflow, dirty coils, or faulty parts, can also be to blame.

Keep reading to find out the eight most likely reasons your dehumidifier is freezing up and how to fix each of them.

a woman checking why the dehumidifier is freezing up

Why Does My Dehumidifier Keep Icing Up?

A dehumidifier freezes up when the moisture hitting the condenser coils turns to ice instead of liquid water. There are many reasons why your unit does this. Here are the eight of the most common causes.

Low Temperatures

Most portable dehumidifier units are made to operate at temperatures above 65 degrees. When the air in the room is colder than this, it causes some of the moisture that condenses on the coils to turn to ice. As ice builds up, the air around the coils gets colder, causing more ice to form.

This cycle can quickly freeze up your dehumidifier and cause it to shut down. 

It is important to shut off your dehumidifier when temperatures in your home fall below 65 degrees. Placing your unit in warmer rooms, such as on the upper floors or away from AC vents, can allow you to run the unit more often, even if some rooms in your house are below that threshold.

Poor Air Flow

a woman checking the dehumidifier’s filter

Your dehumidifier needs a constant flow of air over the coils to work properly. This moving air keeps the coils from getting too cold. If the airflow is restricted, cold air will congregate around the coils and cause ice to form.

Note: The most common reason for poor airflow is a dirty filter. 

Most dehumidifiers have a washable screen filter meant to catch hair and other large particles to keep them from going into the unit. You need to frequently clean these filters to avoid airflow blockages. Some units may have fiber filters that can’t be washed and must be replaced.

Another common cause of reduced airflow is the poor placement of your unit. The area around the air intake and exhaust area needs at least 6 inches of space to maintain proper airflow. 

If your unit is too close to a wall or furniture, it will struggle to move enough air to keep temperatures balanced inside.

Dirty Coils or Fan

Even with a well-maintained filter, finer particles like dust and dirt can get into your dehumidifier and gunk up the coils and fan. When layers of grime build up on these parts, their effectiveness is reduced.

Before checking the inside of your unit for excess grime buildup, unplug your dehumidifier first. Open the housing and examine the coils and fan. If there is visible build-up, you can use your vacuum’s brush attachment to clear away any loose debris. For stuck-on grime, use a damp rag to wipe everything down.

Broken Blower Wheel

The blower wheel is an important part of the fan system inside your dehumidifier. This piece, along with the fan blades, facilitates the movement of air over the coils. If the blower wheel or fan can’t move due to grime build-up or mechanical malfunction, then the coils will freeze up.

Note: When checking the inside of your unit for excess grime, be sure to check the blower wheel. You’ll also want to take some time to manually rotate the wheel and fan to assure both parts can move freely.

Once the unit is clean and put back together, turn the unit on and feel for airflow from the exhaust vent. A mechanical malfunction is probably to blame if the air is still not moving freely through the unit. The most likely candidate in this situation is a broken blower wheel.

Broken Fan Motor

a technician disassembling a dehumidifier

If the problem is not your blower wheel, then a broken fan motor is the next most likely cause.

The fan motor is key to the entire airflow system inside your dehumidifier. If this piece isn’t working, neither the fan nor the blower wheel will turn. When this part fails, it tends to do so with a lot of noise, making it easy to diagnose the problem.

To test your fan motor, turn your unit to fan only and put your ear up to the exhaust vent. If the fan hums or makes any unusual noises, a failing fan motor is likely to blame. If the fan doesn’t kick on at all, then the motor is likely already dead.

In either case, you will need to replace the motor or take the unit in to be repaired.

Faulty Humidistat

close up picture of a dehumidifier’s control panel

The humidistat inside your dehumidifier allows your unit to turn off when the desired humidity level is reached. If this sensor is faulty, the compressor will continue to run indefinitely. The longer the compressor runs without a break, the more likely the unit is to ice up.

One easy way to test your humidistat is to use a separate hygrometer to monitor the humidity level in the room. If the reading between your hygrometer and dehumidifier screen is different, a faulty humidistat is likely the issue.

Even if the reading is correct, the connections between the humidistat and compressor can be faulty. If the unit continues to run even after the reading falls below the target humidity level, this is likely the case.

Either way, you will need to replace the humidistat and associated connections to fix the problem.

Malfunctioning Bi-Metal Thermostat

Some dehumidifiers, especially whole house units, have bi-metal thermostats. These gauges read the temperature of the evaporator and shut down the compressor when this temperature drops too low. This allows the fan to run alone to melt the ice that’s accumulated on the coils.

If the thermostat is faulty, then the reading from the evaporator will be inaccurate, leading to the compressor continuing to run even as ice begins to form.

Note: If your dehumidifier has a bi-metal thermostat and the compressor in the unit continues to run even when ice is visible on the coils, then a faulty thermostat is the culprit. 

Low or Depleted Refrigerant

Like other cooling appliances, dehumidifiers rely on freon to cool the condenser coils. Over time, leaks can develop in the system, causing the refrigerant to run low.

Without the right amount of freon in the coils, a pressure change occurs in the system that can lead to it freezing up. If you have an older unit and all the internal parts are clean and appear to be operating normally, then low refrigerant may be to blame.

If you suspect this is the problem with your unit, call a qualified maintenance specialist to recharge the system.

Dehumidifier Upkeep Best Practices

Many of the issues above can be avoided with proper care of your dehumidifier. To keep your system running smoothly and avoid freeze-ups, you should:

  • Operate only at temperatures above 65 degrees. Be sure to place your dehumidifier in a warm area of your home. If your unit doesn’t have an internal thermostat, manually turn it off at temperatures below 65 degrees.
  • Keep the filters clean. Make a point of vacuuming out or washing your reusable filter screens every few weeks or more. Replaceable filters should be replaced as soon as they become visibly dirty.
  • Ensure optimal placement. Make sure there is plenty of space around your dehumidifier when it’s in use. Six inches is the minimum space you’ll need to maintain around the vents of most units.
  • Keep the inner workings clean. Take time to vacuum and wipe down the coils, fan, and internal components of your dehumidifier every couple of months. Units used in dusty environments like crawlspaces and basements may need this done more often.
  • Don’t short cycle your system. Each time you turn your dehumidifier on, you should allow it to run for at least ten minutes before turning it off again. This gives the unit time to effectively run condensate off the coils and into the drain or reservoir. 
  • Empty the reservoir frequently. If the unit doesn’t drain on its own, be sure to check the reservoir frequently and dump it as needed. If the reservoir gets too full, the unit will shut down.

To learn more about steps you can take to avoid having your dehumidifier freeze up and extend your unit’s life, check out the video below.

Replacing Your Dehumidifier

Many of the problems listed above can be fixed by adjusting how you use your dehumidifier or by replacing malfunctioning parts. But, if none of these DIY repairs work, resolving the issue may take more time and effort than it’s worth. 

In this case, your best bet may be to replace the unit with a new product.

We’ve got some great recommendations for you if you’re in the market for a new dehumidifier. For a new personal or bathroom dehumidifier, check out our articles on the best bedroom dehumidifiers and the best mini dehumidifiers.

If you need to replace a whole-house dehumidifier or consider upgrading to one of these larger models, you’ll want to read this article first. 

Not willing to give up on your old dehumidifier but still struggling to diagnose the issue causing it to freeze up? Drop your questions in the comments section below, and we’ll happily help you problem-solve the issue.

About The Author

Sara Seitz is a freelance writer and novelist. She lives with her husband and wildling toddler in Colorado where she spends her days working on their house, gardening, and reconnecting with nature.

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