Why does dehumidifier freeze up?

dehumidifier fan blades

Is your dehumidifier freezing up and no longer working? There could be many reasons why this is happening, not just because of the cold weather. In this article, we answer the question “why does dehumidifier freeze up” and offer suggestions for repairs to fix this issue.

We’ve researched the reasons and spoken to dehumidifier repair experts to give us an insight into the causes of a dehumidifier icing up, including the cold weather, humidity controls, faulty coils and other reasons.

What happens when a dehumidifier freezes up?

You know that a dehumidifier is freezing up because the coils are covered in ice, causing the dehumidifier to not work properly or to even stop.

By running a dehumidifier as it freezes up, the motor needs to work harder to keep the unit operating which can cause it to overheat.

Dehumidifier freezing up in winter

The first thing that comes to mind when a dehumidifier freezes up is that it’s something to do with the weather, especially if you’re using a dehumidifier in winter.

However, dehumidifiers are more commonly used in the summer than in the winter. A dehumidifier is used to reduce the moisture levels in a room and to bring down humidity. While places such as basements, garages and crawl spaces can be humid all year round, if you use a dehumidifier in other parts of your home, you’re most likely using it in summer.

Dehumidifiers should be run at temperatures above 65 degrees Fahrenheit. Anything below this, and the dehumidifier could stop working.

However, as we mentioned, most people use dehumidifiers at temperatures above this, because this is when humidity levels start to increase and the moisture in the air becomes a problem.

Why does ice form on the coils of a dehumidifier?

When looking at why ice forms on the coils of a dehumidifier, we need to go back to basic science and the rules of condensation and states of matter.

A refrigerant dehumidifier, more commonly known as a compressor dehumidifier, works a lot like your refrigerator in that it has cold coils that help remove moisture from the air before the air is reheated and dispersed into the air as dry vapor.

Ice forms on the coils of a dehumidifier when the air temperature in a room is under 65 degrees. This occurs because as the air passes through the dehumidifier via the vent, the cold metal coils of the dehumidifier condense the air. This turns the air into water droplets that end up in the dehumidifier bucket. This process occurs normally when the room temperature is above 65 degrees.

When the room temperature is below this, the air doesn’t condense into water droplets but turns into ice. Air typically turns into ice at temperatures below 32 degrees Fahrenheit.

Condensation is the process of turning one state of matter into another- either turning air vapor to liquid or to a solid state. A dehumidifier uses condensation to turn air into liquid. Condensation occurs when warm air hits a cold surface, causing the warm air to turn into water droplets.

Problem: Dehumidifier freezes up during winter
Do not use the dehumidifier if the temperature is below 65 degrees Fahrenheit (which is around 18 degrees Celsius).

Faulty humidity control sensors

A humidity control, also known as a humidistat, is similar to a thermostat in that it measures the humidity levels in a room just like a thermostat measures and controls the temperature levels in a room.

The humidity control powers the compressor circuit, allowing it to operate and to stop operating. The compressor shuts off when the humidity level drops too low, which prevents the dehumidifier from freezing up.

If the humidity control is faulty, it can’t power the compressor circuit and so the compressor will not shut off when the humidity level has dropped to below the ideal range.

This fault creates the issue we discussed before about using a dehumidifier when the temperature is too cool, leading to the air turning into ice rather than water droplets, ending with coils that are covered in ice.

You can troubleshoot the humidistat by firstly disconnecting the power to the dehumidifier. Turn the humidistat dial and listen for the click noise that occurs normally when the humidity control is working. If there is no click sound, it may be faulty.

You can also test the humidity control sensor by purchasing a digital hygromter, and comparing the readings on it with the operation of the dehumidifier. If the digital hygrometer and the humidity control sensors are not in sync, then there could be an issue with the humidity control sensor on your dehumidifier (you do need to allow for a slight variation of readings from both devices).

If you’ve figured out that the humidity sensor isn’t working then it needs to be replaced. Either contact a repair man or consider buying a new dehumidifier, which might be more cost effective than getting it repaired!

Problem: Humidity control sensors not working

Solution: Replace the humidity control sensor or buy a new dehumidifier

Faulty Fan Blade

Your dehumidifier has a fan blade that helps circulate the air and prevents the coils from freezing up. If your room temperature is above 65 degrees Fahrenheit and your dehumidifier is freezing up with ice on the coils, then there could be an issue with the fan blade.

When a fan blade stops working, it cannot control the air flow and prevent ice from forming on the coils.

The fan blade should be inspected to make sure there is nothing blocking it from working. Clean the fan blade, the blower wheel and the grille. Before restarting your dehumidifier, manually spin the fan to check that it moves without much difficulty. If it still seems stuck or isn’t spinning properly, it might be faulty and need to be changed.

Problem: Faulty fan blade

Solution: Clean the blades and the wheel, or replace the fan if it is faulty.

Faulty fan motor

The fan motor helps the fan blades work, to control the air flow and temperature of the dehumidifier so that the coils do not freeze up.

When the fan motor stops working, the air flow can’t be maintained and the condenser coils freeze up.

The fan motor should be inspected by an expert repair person and if it needs replacing, it is probably cheaper to buy a new dehumidifier than to get it repaired as the dehumidifier is probably getting old and is outside of the warranty period.

Problem: Faulty fan motor

Solution: Get a repair person to inspect the fan motor and replace, or buy a new dehumidifier.

Faulty bi-metal thermostat

Most dehumidifier models include a bi-metal thermostat which measure the temperature of the air, so that when it drops to below 65 degrees, the fans work without the compressor operating to de-ice the coils. When the thermostat stops working, the dehumidifier can’t determine the air temperature and the compressor continues to operate even when the temperature has dropped, leading to ice on the coils.

To work out if this is the problem, you need to check if the thermostat is making positive contact with the coils and if it is and there is ice on the coils, then the thermostat may be faulty.

Problem: Faulty bi-metal thermostat

Solution: Have a repair person check that the thermostat is working properly before deciding whether to have it repaired or to just buy a new dehumidifier.

Dirty air filter

As part of your maintenance routine, your dehumidifier’s air filter should be regularly cleaned. A build up of dirt or dust in the air filter could cause other issues in the dehumidifier that lead to ice on the coils.

Proper air flow and circulation is needed to make sure that the dehumidifier works properly and doesn’t lead to other issues such as the fan motor breaking down.

Problem: Dirty air filter

Solution: Clean the air filter regularly to make sure it is free of dirt and dust

Air flow disruption

Anything that stops proper air flow can lead to ice forming on the coils. Examples of disruption include putting the dehumidifier too close to the wall or other furniture causing air flow to be blocked, and having objects blocking the ventilation.

Problem: Air flow disruption

Solution: Put the dehumidifier somewhere where there is enough air flow and there aren’t objects that can obstruct ventilation

Electrical and other mechanical faults

If you’ve tried all of the above and your dehumidifier is still freezing up and having ice form on the coils, then there could be other mechanical or electrical faults. This could be from a power surge or an issue with the electrical wiring.

If there hasn’t been a power surge that could’ve caused issues, check if your dehumidifier is still within the warranty period. Check for after sales support from the dehumidifier retailer and see what your options are about getting a replacement.

If your dehumidifier is old (usually more than 5 years old), then consider buying a new one. The cost of repairs alone may not make it worth repairing.

Dehumidifier freezing up: How to fix and prevent this problem

It’s better to prevent ice from forming on the dehumidifier coils in the first place than to deal with ice-covered coils.

Do not operate the dehumidifier when the temperature is below 65 degrees Fahrenheit, otherwise ice will form on the coils. There are some dehumidifiers that are better suited to cold temperatures- invest in one of these especially if you’re using the dehumidifier in your basement.

When ice has formed and the dehumidifier is freezing up, the first thing to do is to switch off the dehumidifier.

Check that the dehumidifier is not too close to a wall, furniture or any other object that could be obstructing the air flow. If you have kids, check if they have inserted an object into the dehumidifier which could be causing the issues. This sort of issue happens a lot!

Check that the filter isn’t causing the issue. Get out your dehumidifier manual and check for how to remove the air filter. Also check if the air filter can be washed- if so, wash the filter and dry it completely before putting it back inside the dehumidifier.

Another option is to vacuum the filter and also vacuum the grille and other parts of the dehumidifier, to remove dust and debris.

While you have the dehumidifier open and you’re removing the filter, check the other components such as the fan blade, wheel and fan motor to rule out any of the other issues discussed in this article.

Not confident in doing this yourself? Never try to repair an appliance without firstly reading the manual and if in doubt, contact a repair man.

If your dehumidifier LCD display shows an error code, this is most likely an electrical issue. Restart the dehumidifier. If it still isn’t working, use a digital multimeter to check the humidistat and bi-metal thermostat to make sure that they are working. The multimeter measures the volts, amps and ohms to see if the appliance is working.

You can also try to clean the coils in your dehumidifier using a vacuum with a brush attachment but before doing so, please check your dehumidifier manual which should explain whether or not you can do this. The coils can be damaged easily, so make sure you know what you are doing.

When your dehumidifier coils are covered in ice, wait for the ice to melt before using the dehumidifier again. Even after trying the recommended fixes in this article, you will need to wait for the ice to melt before trying to start the dehumidifier again.

Long term problems from a dehumidifier that freezes

If you’ve fixed the issue that’s causing the dehumidifier to freeze, keep in mind that there could be long term damage to the dehumidifier.

If you don’t prevent the coils from freezing again, you could end up with faulty parts as the motor and compressor work harder to keep the coils from freezing again.

The overall wear and tear of your dehumidifier will increase and you’ll end up with a dehumidifier that needs to be replaced much sooner than if you were careful in the first place.

Prevention is the best, so avoid using your dehumidifier in cold temperatures. Try to use other methods to dehumidify rooms and spaces that are cold such as your garage and basement, before deciding to use a dehumidifier.

By Christine Carlisle

Christine is a freelance senior writer for Home Health Living and has been writing for us for 4 years. She's a health copywriter with over 10 years experience as a writer. Christine lives alone in a cabin in Maine and was once a hand model while living in New York City. She's a dog person.