Why is My Dehumidifier Freezing Up and How to Prevent It

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In a humid climate, little is more frustrating than having your dehumidifier freeze and stop working. 

Why does this happen – and what can you do to prevent it? 

Excessive humidity can cause damage to your furniture, dampness, promote mold and fungi, and worsen some health conditions and allergies.

This is why it’s critical to take the steps to ensure your dehumidifier functions when needed.

In this short guide, we discuss the most common show-stopper issues with dehumidifiers and the steps to take to prevent and recover from them.

What Causes a Dehumidifier to Ice Up?

There are lots of different factors that come into play. 

Temperature of the room

One of the most common causes of a dehumidifier freezing up is the temperature of the room that it is located in. Most units will work perfectly fine in a room that is 65° F or more. However, if the air temperature drops lower than that, the unit may freeze up and quit working.

The air is pulled into the unit through a vent. As it travels through, the cold metal coils cause the water in the air to condense and drop into a collection reservoir or pumped out through a hose. This works quite well when the temperature is high, but if it gets too cold, the water vapor will freeze instead of condense, which causes problems.

Air flow

Another reason your dehumidifier could freeze up is a restricted flow of air through the unit. 

If your fan is not functioning well or the condenser coils are clogged with dust, air cannot flow through the unit quickly enough to cool and remove excess humidity. 

If you regularly clean and maintain your unit, you’ll find these issues quickly. Then, you can clean the part or replace it as needed before it does harm.

If you have a dehumidifier that is icing up, the first thing to do is to stop using it. If you keep using it while the coils are frozen you will cause further damage.  If air flow is restricted, then the motor & compressor unit will have to work much harder and could get overwhelmed and burn out.

How to Prevent Your Dehumidifier from Freezing

There are several things that you can do to keep your dehumidifier from freezing up—and to defrost it if it does.  

The most common culprits include:

Humidistat

If your dehumidifier coils are freezing while room temperature is higher than 65°, then you may have a problem with the unit’s humidity control unit, also known as a humidistat

A humidistat is a lot like a thermostat, in that it constantly monitors the level of humidity in the room so the unit can turn itself on and off to maintain a set level in the room. The electrical contacts of a humidistat cause the compressor of your dehumidifier to turn off and on. If the humidistat is not functioning properly, your compressor stays on too long and causes the coils to freeze.

In addition, the electrical contacts in a humidistat can get deformed or covered with a conductive layer of dust, which leads to the same issue. 

In order to troubleshoot your humidistat, you’ll want to first disconnect the power to your unit. 

Then, turn your humidistat dial and listen for the clicking noise that indicates it is functioning properly

In addition, you can test for a short in your humidistat using a multi-meterWhen you rotate the control, the contacts need to at some point make an open circuit (no current flowing). If they do not, you need to replace the humidistat.

Blower Wheel / Fan Blades

If the humidistat is not the issue, then you may have a problem with your blower wheel/fan blade. 

These parts control the flow of air through the unit that is required to prevent the condenser coils from freezing up. 

If you’ve cleaned/replaced the air filter, but there is no air flowing through the grill, you should remove the fan cover to inspect the coils.

Take the time to clean off any dirt/debris on the blades that could be preventing air flow. 

Then, check the fan blade/blower wheel to make sure that there’s nothing preventing free movement. If wheel or blades appear to be damaged, you’ll want to replace them. 

If not, then take the time to carefully clean them. 

Fan Motor

If neither the humidistat nor the fan are damaged, then the issue may be a faulty or dying fan motor.  When a fan motor is damaged, it will often make a high pitched noise indicating mechanical failure and/or a burned electrical smell indicating a short inside the unit.  

In both cases, the only fix is to replace the motor entirely – do not attempt to fix it.

1 thought on “Why is My Dehumidifier Freezing Up and How to Prevent It”

  1. Floyd Arthur Miller

    The room temp. is 68deg. , the fan is running on high and working fine. I shut it off and let it defrost for 2 days and it worked for a day and froze up again. It never stops running. Thank you!

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