Why Do Dehumidifiers Ice Up: Understand Dehumidifier Freeze-Ups

By: Evan Scoboria, Last updated: June 28, 2023

Dehumidifiers are essential household appliances, especially in areas prone to excessive humidity. These devices work tirelessly to maintain a comfortable and healthy environment within your living space. However, despite their undeniable usefulness, dehumidifiers can occasionally freeze up, leaving you wondering why. In this article, we'll explore the reasons behind dehumidifier icing and provide you with practical solutions to defrost your device and prevent future freeze-ups.

Iced Over Dehumidifier Coil

Why Dehumidifiers Ice Up

Low Room Temperature

Dehumidifiers are designed to operate effectively within a specific temperature range, typically between 60 and 85 degrees Fahrenheit. When the room temperature drops below this range, especially to around 60 degrees Fahrenheit or lower, the cooling coils of the dehumidifier can get too cold and cause condensation to freeze on the coils, leading to an icing issue.

How does this happen? Well, dehumidifiers pull in warm, moist air and cool it down. This cooling process causes the moisture in the air to condense and collect in the water tank, reducing the overall humidity in the room. However, if the room temperature is already low, the coils can become excessively cold, leading to condensation freezing on the coils instead of being collected in the tank.

Consider warming up the room or moving the dehumidifier to a warmer location to prevent freezing. If this isn't possible, dehumidifiers on the market are designed to work efficiently in lower temperatures, often referred to as "low temp" or "basement" dehumidifiers.

Airflow Restriction

Dirty Air Filters

Air filters in dehumidifiers are designed to catch dust, allergens, and other airborne particles, ensuring that the air circulating within your space is clean and safe. However, when these filters get dirty and clogged with grime and debris, it restricts the airflow across the cooling coils. Counter-intuitively, when your dehumidifier is experiencing this issue, it may start blowing hot air while the coils are freezing internally. This is caused by the motor and fan having to work overtime to try to move air through the machine.  

For a dehumidifier to function correctly, it needs a constant flow of warm, moist air to be drawn over the cooling coils. If this airflow is limited due to a dirty air filter, the coils can become too cold and start to freeze up, leading to ice formation.

Keeping your dehumidifier’s air filter clean is critical. Most manufacturers recommend checking and cleaning the air filter every two weeks, but this frequency might need to be increased if the dehumidifier operates in a particularly dusty environment.

Cleaning the filter usually involves removing it from the machine and gently washing it with warm water and mild soap. After cleaning, dry the filter thoroughly before reinserting it into the dehumidifier. Refer to your device's user manual for specific instructions on how to clean its air filter.

You may need to replace the filter if it is damaged or extremely dirty. Replacing air filters regularly will help maintain the efficiency of your dehumidifier and prevent the ice buildup issue.

Blower Fan or Fan Issues

Problems with a dehumidifier's blower fan or fan motor can also contribute to ice buildup. The fan draws warm, moist air into the dehumidifier and over the cooling coils, and the fan then circulates the cooled air back into the room.

The airflow across the coils is restricted or halted if the fan or fan motor malfunctions. This means the coils remain cold and stationary, which can lead to condensation forming and freezing on the coils, hence causing icing.

Common signs of fan or fan motor issues include a dehumidifier running but not blowing much air, making unusual noises, or not spinning at all.

Fixing a fan issue can be as simple as cleaning dust or debris off the fan blades. However, if the motor is faulty, it may need to be replaced. It's important to consult a professional or refer to your dehumidifier’s user manual for specific instructions, as a fan and fan motor replacement can be complex and potentially hazardous if not done correctly.

Faulty Humidity or Temperature Sensor

A faulty humidity or temperature sensor in your dehumidifier can also lead to icing issues. These sensors work in tandem to monitor the conditions in the room, informing the dehumidifier when to start and stop extracting moisture from the air.

The humidity sensor, also known as a hygrometer, measures the air's moisture. If this sensor malfunctions, it may read the humidity levels inaccurately and can cause the dehumidifier to run continuously, even when the desired humidity level has been reached.

On the other hand, the temperature sensor gauges the ambient room temperature. If it's faulty and reads at a higher temperature than actual, the dehumidifier may run in too cold conditions, leading to ice forming on the coils.

Both of these situations lead to overcooling and, subsequently, freezing. This is why regular maintenance and inspection of these sensors are crucial to ensure they are in good working condition.

If your dehumidifier has a faulty sensor, it may need replacement. For this, it's best to consult a professional unless you're comfortable and familiar with electronics repair. It's worth noting that tampering with the device could void any existing warranty, so always double-check before deciding to DIY a repair.

Refrigerant Leak

A refrigerant leak in your dehumidifier can occur due to several reasons, such as general wear and tear, corrosion, physical damage to the unit, or faulty manufacturing. The refrigerant, a crucial component in the operation of your dehumidifier, circulates through the coils. As it transitions from a high-pressure gas to a low-pressure liquid, it absorbs heat from the surrounding air and collects moisture, thus reducing the humidity.

If the refrigerant starts leaking, the amount of refrigerant available to cool the coils decreases. This reduction can cause the remaining refrigerant to supercool the coils leading to a rapid temperature drop below the dew point, causing the humidity from the air to freeze and form ice on the coils instead of condensing into water.

Besides ice build-up, other signs of a refrigerant leak can include the dehumidifier not effectively reducing the humidity level in the room, the unit running for extended periods than usual, or strange noises coming from the dehumidifier.

If you suspect a refrigerant leak, it's essential to turn off and unplug your dehumidifier immediately to prevent further damage. I suggest contacting a professional technician for a diagnostic and repair, as mishandling refrigerants can lead to health hazards and environmental harm due to their chemical properties.

How to Defrost a Dehumidifier

Unplug and Empty the Dehumidifier

Unplugging and emptying the dehumidifier are the first steps you should take when dealing with a frozen dehumidifier. It's not just about safety (although that's a big part); it's also about ensuring that the dehumidifier doesn't continue running while it's frozen, which could potentially damage the unit.

When you notice that your dehumidifier has frozen up, here's what you should do:

  1. Switch off the dehumidifier: Don't just leave it running in the hope that it'll thaw out on its own - this can cause further issues. Instead, turn off the machine immediately to prevent additional icing and stop the fan from blowing more air over the frozen coils.

  2. Unplug the machine: This is essential for safety reasons. Unplugging the device eliminates the risk of electrical shock when dealing with the unit.

  3. Empty the water tank: Even though the unit is frozen, water may still be in the collection tank. Be sure to empty this as it might spill when moving the unit.

Place the Dehumidifier in a Warm Room

Once you've unplugged and emptied your dehumidifier, the next step in defrosting it is to move it to a warmer location. This is essential, especially if the freezing is due to a low room temperature.

The idea here is simple - warm air will help melt the ice faster. To do this:

  1. Find a warm spot: Look for a warm room in your house, preferably one consistently above 60 degrees Fahrenheit (15 degrees Celsius). This could be a room that gets a lot of sunlight or one where there's a heat source, such as a kitchen or laundry room.

  2. Relocate the dehumidifier: Carefully move your dehumidifier to this location. Remember, the unit may be heavy, and there's a chance of some water from the melted ice spilling, so be careful not to slip or drop the unit.

  3. Leave the dehumidifier to warm up: Allow the dehumidifier to sit in the warm room until all the ice has melted. This process can take a few hours.

Use a Hair Dryer to Melt Ice

Using a hairdryer to melt ice off your dehumidifier is another method that can be used, but it needs to be done with great care and patience.

The basic steps are as follows:

  1. Safety First: Make sure the dehumidifier is unplugged and moved to an area where it's safe to use the hairdryer. Avoid areas with puddles of water or wet floors.

  2. Set the Hairdryer: Set your hairdryer to a low or medium setting to prevent damage to the plastic components of your dehumidifier. The high heat from the hairdryer can warp or melt the plastic if used in a high setting for an extended period.

  3. Slow and Steady: Start from the top and work your way down slowly over the coils. Be careful not to blow hot air directly into the motor or electronic parts, and never use the hairdryer to melt ice inside the machine where you can't see it.

  4. Dry It Out: Once the ice is melted, dry out the machine as much as possible to prevent any electrical short circuits. This can be done by leaving it in a warm, dry area or using a towel to blot excess moisture.

Clean the Dehumidifier Before Use

Cleaning your dehumidifier before you put it back into use is critical to maintaining its effectiveness and longevity. Leftover moisture can encourage mold and bacteria growth, so ensure the unit is clean and dry before plugging it back in. Here's how to do it:

  1. Empty the Reservoir: If your dehumidifier has a collection reservoir, ensure it's emptied. Any leftover water can become a breeding ground for bacteria.

  2. Clean the Reservoir: Use warm, soapy water to clean the collection reservoir. A mild detergent should be enough to remove any dirt or grime. If there are any signs of mold or mildew, a bit of vinegar or a mild bleach solution can help to kill the spores. Be sure to rinse thoroughly.

  3. Clean or Replace the Filter: Check the filter in your dehumidifier. If it's dirty, you'll need to clean or replace it according to the manufacturer's instructions. A clean filter is crucial for effective operation.

  4. Wipe Down the Exterior: Use a damp cloth to wipe down the dehumidifier's exterior, removing accumulated dust or dirt.

  5. Let it Dry: Before you plug your dehumidifier back in, make sure it's completely dry. Any leftover moisture could damage the appliance.


Dehumidifier icing can be frustrating, but understanding the causes can help you resolve and prevent it in the future. By paying attention to room temperature, ensuring proper airflow, maintaining the unit's cleanliness, and monitoring the condition of its sensors and refrigerant, you can keep your dehumidifier running smoothly and efficiently. With a well-maintained dehumidifier, you can enjoy a comfortable and healthy environment free from excess moisture and humidity.