Why Your Dehumidifier Is Blowing Out Cold Air – And How To Fix It

Dehumidifiers will blow cold air because of ice build-up on the coils, a broken compressor, low refrigerant, or a clogged air filter. A faulty circuit board, thermostat or bucket switch can also cause a dehumidifier to blow out cold air. Dehumidifiers will also temporarily blow out cold air when in the defrost mode.

Dehumidifiers are an essential part of our homes, especially during hot and humid summers. But one of the most common technical (and frustrating) problems is a dehumidifier blowing out cold air.

This troubleshooting guide takes you through all the possible reasons your dehumidifier might be blowing out cold air and give you quick fixes for each one.

7 Reasons Why Your Dehumidifier Is Blowing Cold Air

A dehumidifier absorbs moisture from the surrounding air, and normally emits dry, warm air. Unfortunately, faulty parts can make it produce cold air instead.

Here are all the reasons why your dehumidifier could be blowing out cold air:

1. Frost and Ice Build-up

Frost or ice can build-up on the coils of the dehumidifier if the temperature in your home is lower than normal or if there’s a disruption or reduction in air flow.

Note: This only applies to refrigerant or whole house dehumidifiers – not desiccant ones.

You can easily notice the frosting on the coils, and some of the ice is often visible on the outside of the unit.

Dehumidifiers operate best when the air temperature is between 70 and 90 degrees Fahrenheit, if the temperature drops below 65 degrees the coils can start to ice up – and the unit will begin to blow out cold air.

Accumulation of dirt, debris, and damage to the blower wheel or fan blade prevent effective airflow, which also eventually leads to ice build-up.

Solution:

• Confirm the temperature of the ambient air is within the optimal operating temperature of 70-90 degrees Fahrenheit
• Defrost the dehumidifier
• Gently removing any dirt, debris or mineral build-up from the dehumidifier, especially the fan
• Ensure the fan and blower wheel are firmly attached (not loose)
• Replace the fan or blower wheel if damaged.

2. Broken Compressor

A compressor is a vital part of both refrigerant and whole house dehumidifiers, as it helps take the moisture from the air.

It works together with the fan and refrigerant, to draw in moist air and cool it down once it meets the cold surface of the coils.

In normal conditions, the compressor pressurizes the refrigerant, converting it to gas. The refrigerant gases absorb the moisture from the air and then pass over the coils, condensing into a liquid. The water then drips into a tray, bucket or hose, depending on your model.

However, any fault with the compressor means the dehumidifier can’t function properly, and eventually, it will blow cold air.

This problem can easily be identified if your dehumidifier starts with a clicking sound.

Solution:

• The only solution to the issue is to replace the compressor.
• Hopefully your warranty is still valid. But if not, it’s usually better (and cheaper) to buy a new dehumidifier instead.

3. Low Refrigerant

Refrigerant is the chemical that’s compressed into a gas inside the dehumidifier, where it then draws in moisture from the air, before it is cooled, condensed and collected in the drip tray, bucket or hose.

Low amounts of refrigerant mean the moisture from the air can’t condensate inside the unit and cold, but humid air is blown back into the room.

To see if there’s a problem with the refrigerant, check the cooling coil. In normal conditions, the coil should be cool to touch.

If that’s not the case, refrigerant is possibly low in the system. The refrigerant (often Freon) may be replaced, however the root cause might be that the refrigerant is leaking out of the system.

If this is the case identifying the broken point in the coils is the key.

If the refrigerant is leaking, fixing the problem may not be cost-effective. So if it is not in warranty, it is better to buy a new one.

Solution:

• Refill the refrigerant using a filler pipe.
• If the refrigerant is leaking, you can replace the coils. However, on smaller stand-alone units it is often cheaper to replace the dehumidifier.

Condensation dehumidifiers need refrigerants, such as Freon, to draw the moisture from the air, without which dehumidification wouldn’t be possible. However, simple evaporative dehumidifiers don’t require refrigerant as they rely on chemical absorbents to remove the moisture.

How To Refill The Refrigerant In a Dehumidifier

Refrigerant in a dehumidifier can be refilled in small thrusts using a filler pipe. Remove the outer case, detach the valve cover, attach the filler pipe and then fill in the refrigerant. Once done with the process, remove the pipe and re-assemble the system.

Over the period, some amount of refrigerant leaks through the system. To ensure that your device delivers the best performance, you need to recharge, i.e., refill the refrigerant after long periods of time.

Here’s a step-by-step guide on refilling the refrigerant in your dehumidifier:

• Remove the valve cover and check the refrigerant level.
• In the process, make sure that excess air is removed from the filler pipe to protect the compressor from damage.
• If the refrigerant level is low, attach the filler pipe and refill it.
• Make sure you do so in short bursts to avoid overfilling.
• Once done, remove the pipe and close the valve.

Remember to check your manual and use a refrigerant compatible with your appliance.

4. Circuit Board

Just like any electrical device, any issue with the dehumidifier’s circuit will prevent proper relaying of the current. The device won’t work properly and it will release cold air.

A PCB (printed circuit board) is the power supply for compressors and fans. If this control board has a problem, the dehumidifier will not work properly.

Check if all other parts of the dehumidifier are working fine. If you don’t find any underlying fault in the compressor or coils, then it is likely the circuit is a problem. Unfortunately, this is a common problem for dehumidifiers.

Solution:

• Replace the control board. You can also take it to a repair store or have a professional electrician fix it for you.
• Invest in a new dehumidifier (this is often the cheaper option).

5. Faulty Thermostat or Humidistat

Dehumidifiers have a humidistat and thermostat to help regulate the humidity and temperature of the room. Since the unit takes in moisture and releases warm air, it can cause the room temperature to rise slightly. In this scenario, a humidistat is what lets you control the extent of moisture filtration.

It’s designed so you can set the humidity to their own comfort level. Once the humidity reaches that point, the humidistat kicks the system in a cooling cycle. This is done to reduce the room temperature and bring the relative humidity levels back to the set point.

If the sensor is faulty, it can result in the humidistat malfunctioning and cold air blowing instead.

Solution:

• The easy and only possible fix for the issue is to replace the humidistat with a new one. For large systems, any brand of humidistat will do.
• If your dehumidifier is a stand-alone unit (not part of a HVAC), you may need to replace the dehumidifier

6. Bucket Switch

The dehumidifier condenses the air and converts the moisture into liquid form. This water is then collected in the bucket (or tray) and is drained out through a hose (or requires manual removal).

There is a switch near the bucket that activates the float mechanism. This means that when the bucket is full, sensors are activated, and the dehumidifying process stops until all the water is drained.

This prevents water from overflowing.

When the bucket switch isn’t working properly, the dehumidifier won’t be able to sense the water level in the bucket. If this issue kicks in when the appliance is in defrost mode, you will have cold air continuously blowing out of the system.

Check if the float switch is connected to the assembly. If all the connections are in place, use a multimeter to identify the exact point where the problem is arising.

Solution:

• Replace the float switch. This is relatively straightforward and can bring the system back to working normally. Most float switches can be easily purchased from Amazon.

7. Clogged Air Filter

Although dehumidifiers mainly reduce the moisture in the atmosphere, many also have an air filter that cleans the air of any large particles of debris, dust, and other contaminants. You can find it at the back of the grille.

If not cleaned properly, this filter gets clogged over time. As a result, the unit isn’t able to perform properly. This can also cause other mechanical issues, and dehumidifiers can start pumping out cold air.

Ideally check your air filter for any possible clogging at least once a week when using your dehumidifier regularly. If you see any dust or other particles blocking the filter, cleaning it will solve any problem that you might be encountering.

Solution:

• Regularly clean the filter
• Replace filter if dust, dirt or mineral deposits have built up on the filter.

To clean the filter, unplug the device and take the filter out, and vacuum it to remove the dust.

If it’s a washable filter rinse it thoroughly with soap and water. Let it dry, and then place it back in the dehumidifier.

If you leave the filter as is, the dirt and dust harden, and it becomes difficult to wash them off. Therefore, we suggest weekly cleaning the filter to prevent any issues, especially when the dehumidifier is running frequently or if you have hard water.