Why Your Dehumidifier Runs But Doesn’t Collect Water

It would be useful to start with some information on how the basic process occurs. Compressor-type dehumidifiers pull room air through an array of cold evaporator coils. As the air temperature drops, the water vapor in it starts to condense on the coil surface in the same way as water droplets form on the outer surface of a cold glass on a humid day. The resulting water accumulates in a tray or a tank placed under the coils. A sensor known as a humidistat monitors the relative humidity of the surrounding air and signals the compressor to start and shut down.

When users talk about their dehumidifier not working but making sounds, they refer to its fan and compressor operating correctly while the tank remains empty. This may indicate two entirely different situations: the first one is that there’s no water vapor left for the dehumidifier to remove from the air (and this is not a malfunction at all). The second one means that some other factor prevents the process of moisture removal. Proceeding through the following causes of such problems in order will help determine which case applies to your situation.

Cause #1: Humidity Setting Is Already Satisfied

One very likely explanation as to why your dehumidifier seems to be running without gathering water is because there really is nothing left for it to gather. All dehumidifiers have their set target of humidity, which is usually around 45-50% relative humidity. Once this target is reached, the humidistat will tell the compressor to shut off, although it may still run its fan to continue checking the air.

In case your room is already dry due to whatever reasons, be it because the dehumidifier did its job in the last 24 hours or because the weather has changed, having no water in the tank is perfectly normal.

How to fix it?

• Purchase a basic standalone hygrometer and put it several feet away from the machine, at about the same level as its air intake.
• Compare this value with what is displayed on your dehumidifier.
• When the independent reading is either equal to or below the set point, the device does its job.
• For the continued operation of the appliance, reduce the target humidity by five to ten percent and observe whether the compressor restarts.

Cause #2: The Room is Too Cold for Condensation

For dehumidification, the devices utilize temperature differences between the air coming into them and the coil surface. When the room where such a device operates is constantly colder than 60-65°F – which is rather typical for unheated basements, garages, or crawl spaces – the temperature of the coil can fall below the freezing point before any condensation occurs.

How to fix it?

• Look up the minimum rated operating temperature in your dehumidifier’s owner’s manual.
• Normal compressor-type dehumidifiers are not made to work in spaces that remain below 65°F.
• If your room usually runs cold throughout the year, a low-temperature or desiccant dehumidifier is what you need. This type of dehumidifier does not use any refrigerant coils, so it will be much more efficient.

Cause #3: Clogged Air Filter

All dehumidifiers have a filter system that works by pulling in air from the space and filtering it before directing it towards the coils. The moment that filter gets clogged with dust or hair, the amount of airflow that reaches the coils becomes limited, resulting in less moisture being collected by the dehumidifier.

A clogged air filter is one of the main reasons why dehumidifier coils freeze. That is because a clogged filter restricts airflow, allowing the coil temperature to drop below freezing point even though the room is warm enough.

How to fix it?

• Remove it and hold it up to the light source – if there is no light visible, you need to clean it
• Soak it in a mild solution of soap and water and then rinse it
• Let it dry completely before putting it back in place
• The filter should be cleaned every two to four weeks during periods of intensive operation, as recommended by manufacturers

Cause #4: Frozen or Dirty Coils

If opening up the front panel reveals that there is a layer of frost/ice on the coils – that’s what’s going on. As soon as the ice forms, it becomes an insulator, which means the coil is unable to come into direct contact with the air flowing inside of it. This way, while the unit continues working and the fan keeps blowing air, the condensation process stops working and very little moisture gets collected in the tank. Frosted coils are a downstream effect of one of the causes mentioned earlier – clogged/dirty filter, blocked airflow, lack of refrigerant or too cold room temperature.

How to fix it?

• Shut down the unit and let the coils defrost (this might take several hours)
• Then inspect the coils for any dirt/mold/debris
• Gently clean the coils using the coil cleaning solution and a brush
• Deal with whatever was causing the problem – clogged/dirty filter, blocked airflow, lack of refrigerant or too cold room temperature

Cause #5: Damaged or Worn Out Humidity Sensor

The humidistat is the element that triggers the compressor activation. In case it gets clogged with dust or gets out of calibration, it will provide a false reading regarding the humidity of the air. So instead of detecting the level of humidity in the room and activating the compressor, the humidistat will tell the control board that the air is already dry, thus triggering fan operation while neglecting the actual moisture content of the room.

How to fix it?

• Gently wipe the sensor with a soft, dry cloth or a blast of compressed air, being careful not to touch the sensor itself Refer to the manual for any recalibration instructions, which vary by brand Rerun the dry towel test after wiping to ensure the sensor is responding properly
• If it still does not respond, replacement will be necessary, and it may have to be performed by a professional in some cases

Cause #6: The Dehumidifier Has a Continuous Drain Hose Connected to It

In case your dehumidifier has a continuous drain feature, and there is a hose connected to it from the back side, then the unit is not depositing the condensed water into the tank but is diverting it into the hose, and then to a drain pipe, sump pump, or outside. Checking the water tank in such a case will show that it is completely empty while the unit is doing its job perfectly fine.

This is perhaps one of the few reasons on this list that is not associated with the problems in the dehumidifier itself.

How to fix it?

• Look at the back side of the unit for a drain port and a hose
• If there is a hose connected, follow it and make sure it leads the water somewhere useful and is not bent or disconnected anywhere along its way
•  Or, if you wish to monitor the water removal process yourself, simply disconnect the hose Don’t forget that now you’ll have to empty the tank by hand

Cause #7: Low Refrigerant or Refrigerant Leak

The refrigerant is responsible for allowing coils of a compressor-type dehumidifier to cool to such a degree where the condensation can occur. If the refrigerant amount in the unit is insufficient either due to a slow leak or a manufacturing defect, the coils will not be able to reach the required temperature, resulting in poor moisture removal despite the compressor running.

The warning signs are a hissing noise coming from the device, oil marks in the fittings, and icing up of the coils even when there is no very cold ambient air in the room.

How to fix it?

• Be aware that any issue with refrigerant cannot be fixed by yourself
• Understand that the manipulation of the refrigerant requires specific equipment
• Contact a certified HVAC technician to help with the refrigerant problem if it occurs

Cause #8: Airflow Around the Device Is Obstructed

Dehumidifiers require a clear access to the air to perform properly. If the machine is put in the corner or near a piece of furniture or other obstacles, the airflow through the intakes and exhausts will be significantly reduced. The lack of air means that less humid air will be drawn through the unit, and the device will have to operate with increased difficulty, eventually overheating or shutting itself down.

How to fix it?

• Make sure that there is at least 12-24 inches of free space around the entire dehumidifier, as it is recommended by most manufacturers 
• Move the machine in such a way that the intake and exhaust vents are not obstructed by anything Make sure that grilles and filters are not clogged by dust particles

Cause #9: Compressor Failure

If none of the other possible causes listed above explain why the system isn’t collecting water, then the compressor is likely the culprit. If the compressor isn’t operational, then the coils won’t be getting cold and there will be no condensation at all, no matter how long the fan operates. Other symptoms include weird noises (clicking, humming, whirring), faint smells of burning from the unit.

How to fix it?

• Find out what it will cost to repair Compare that number with the cost of a brand new unit. Replacing a compressor is usually the most expensive repair a dehumidifier can require and is comparable to or even higher than the cost of a new unit.
• Get ready for replacement to be the best solution, especially if the unit has been used for a few years.

Cause #10: Electrical or Control Board Problem

The dehumidifier control board serves to organize the work of the compressor, fan, and other systems, as well as displays information about the humidity level. If the board breaks down, then it might cause the unit to act strangely — fan running while the compressor is off, incorrect information, and other error codes.

How to fix it?

• Perform a power cycle — disconnect the device, wait for several minutes, reconnect it — this will help to solve many electrical issues
• Make note of the codes if they appear before and after the power cycle

• If codes remain or problems persist, get the board inspected by a professional who knows your particular model

Conclusion

An empty tank while a dehumidifier works without accumulating moisture does not necessarily indicate that you will have to buy a new device. Follow this list of reasons in the following order: make sure the settings of humidity and the actual temperature of the room indicate the need for dehumidification, clean the filter and coils from any accumulation or ice, and make sure that the dry towel test does not point to the fact that a dehumidifier sensor works incorrectly. In addition to these steps, make sure that the hose drain system works properly without you noticing it and ensure that nothing blocks the flow of air around the device.

These are the last steps you should do by yourself and now you should contact professionals because such problems as refrigerant leaks, compressor failure, or problems with the control board require special attention and repair.

If you experience a problem with a dehumidifier not collecting water but running , professional diagnosis of the device will reveal whether it is damaged internally. If you live in Edmonton and you have to solve this problem, then Getairify.com can become your reliable assistant and help you to fix all the issues with a dehumidifier.