Dehumidifiers are great appliances to control humidity levels. Adequate humidity in your living space increases comfortability and keeps you and your home healthy. When you turn your dehumidifier ON it will run until selected humidity level is achieved. However, what if it keeps shutting off before desired relative humidity is attained? What if your dehumidifier turns on and off constantly during operation?
In this article, I discuss specific reasons your dehumidifier shows this intermittent behavior. I have also covered solutions to these problems for you. Even though I highly recommend a certified technician in some of the cases, it is a great time and money saver if you know the problem beforehand.
1. Temperature Too Low for Dehumidification
Most of the dehumidifiers available in the market operate on vapor compression cycle. This means they use refrigerant for dehumidification process, just like air conditioners.
An airflow is established through the dehumidifier by using a fan. Air comes in contact with the cool evaporator coils of the dehumidifier. These coils are at a temperature lower than due point of the air. Due point is the temperature below which water condenses from air and dehumidification is carried out.
The lower the temperature of the room, the lower is the dew point temperature and the lower is the temperature required by evaporator coils in your dehumidifier in order to extract humidity from air.
However, when the temperature of ambient air is very low, it results in icing of the coils. It is also referred to as the frosting up of the dehumidifier. The ice buildup will cause inhibition of airflow through cooling coils. As a result, airflow rate will be reduced, leading to reduction in dehumidification.
For dehumidifier operation, ideal room temperature is between 70°F and 90°F (21°C to 32°C). Refrigerant dehumidifiers should not be used below 60°F (about 15°C). You should never use a refrigerant dehumidifier below 41°F (5°C)
If you operate it at sufficiently lower than prescribed temperature, your evaporator coils will slowly develop ice. This will deteriorate the dehumidification process and eventually stop it.
Some modern dehumidifiers have auto-defrosting or anti-icing feature. This allows them to automatically turn off the compressor and keep fan running until ice melts.
In a region where temperature is unsuitably low for refrigerant dehumidifier to work, there are two solutions.
- First option is to increase the temperature of the room to be greater than the prescribed limit i.e., 60-degree Fahrenheit. This will prevent frosting of dehumidifier and keep your room at comfortable temperature.
- The second option is to use a different kind of dehumidifier. Go with a desiccant humidifier or a LGR (Low Grain Refrigerant) dehumidifier. Desiccant dehumidifiers are not dependent on room temperature, so you are entirely going to get rid of that problem.
Heating the room is suitable if you live in the room. In other locations of your home, like crawl space, connecting room, basement etc., I recommend you use a desiccant dehumidifier. To save you the trouble of finding it, I selected one for you. Click here for specifications.
2. Dirty Blocked Filter
Air that passes through the dehumidifier is cleaned by an air filter. Some dehumidifiers have two filters for that purpose, one at the intake and the other at delivery/exhaust.
When the filters are unclean and mucky, airflow through them is restricted. As a result, compressor has to work harder in order to sustain the airflow. This causes more energy consumption and heat generation.
This may also cause your compressor to heat up more than it should.
However, a more probable event due to clogged filter is frosting of the evaporator coils. The reason is low flow rate of air.
When the flow rate becomes inadequately low, quantity of air coming in contact with cooling coils will be reduced. As a result, the temperature of the coils will go very low to cause ice buildup.
The dehumidification will be reduced and the dehumidifier compressor will shutoff, going into defrosting mode, to melt the ice.
If your dehumidifier keeps going in defrosting mode and you have not given a check to your filters for a while, then it is highly probable that unclean filter is the problem.
Clean your filters in routine. Some recommend it every week, the others in every three weeks and some after certain hours have passed.
I recommend you look it up in the instruction manual that comes with the product. If you don’t find it there, check the product website or you can contact your dehumidifier manufacturer.
However, if you keep on doing it every week or so, you will get an idea when to clean your filters, depending upon the operation of your dehumidifier.
Some dehumidifiers also have a filter reset indicator light. It turns on after specific number of hours of operation have passed. This duration is set by manufacturer.
The filters in dehumidifiers are almost always reusable, so you will not have to change them. Use lukewarm water to wash the air filter gently. Allow it to dry properly before inserting it back.
3. Inadequate Fan or Blower Speed
Fan is the component of dehumidifier that pushes air through it. The term ‘blower’ is also used interchangeably with fan, mainly depending upon the design. However, both perform the same function i.e., generating forced airflow.
When air comes in contact with cool evaporator coils, heat is taken up by the coils, temperature of air is reduced below dew point and humidity is extracted from it.
The flowrate of air through the dehumidifier needs to be adequate.
With less airflow rate, insufficient air comes in contact will cooling coils. As a result, less cooling will be used up from evaporator coils. This will cause their temperature to reduce to drastically low levels, causing ice buildup in the coils.
Frosting will cause the dehumidifier to go into defrosting or anti-ice mode until ice melts. This will take more time than usual due to lower fan speed.
When ice will melt, dehumidifier compressor will start again. However due to less airflow ice will develop repeatedly. These short cycles will cause more energy consumption for less and incomplete dehumidifier operation and reduced life.
Causes and Solutions of Slow or Non-Operational Dehumidifier Fan
There are three common causes of a slow fan/blower speed or one that is not working:
Blower Motor Is Faulty
One of the causes for a slow blower, especially if it does not start, is a damaged blower motor.
Motor needs to be checked for shortages and continuation. In case motor is the culprit you have two solutions. Either get it repaired or get a new one.
If you discover a complicated internal fault, I personally advice you to just buy a new one. It will save you a lot of trouble. Just remember to properly check the specifications and description before getting a new blower motor. It should be same as the one that was primarily fitted by manufacturer.
Fan/Blower Blades are Damaged
Another reason why required airflow could not be established may be damaged blower blades.
In this case, motor and blower are running at the required RPM. However, not enough air is being pulled by the blades. If you see a broken fragment or any other damage to blower blades, you will have to get it replaced.
I advise you to contact product support to get the recommended certified parts.
Faulty Electronic Components Associated with Running of Fan
There are so many factors involved in running your dehumidifier fan. For example, controlling fan speed, variable switching, operating it with/without compressor etc.
One of the reasons why your fan is running at a slow speed, or not running at all, could be electronic components like switch, capacitor, relay etc.
Tracking the faulty component is not that complicated. Check the current in the entire circuit of the control board. When you find discontinuation of electric current after a certain component, it is very likely it is the one at fault and needs replacement.
I recommend that you only do it if you have experience in this field. Best is to get it check by a certified technician.
I will give you an example by this video I found the other day. It will give an idea about tracking the fault when your dehumidifier fan is not running .
4. Lack of Refrigerant Due to Leakage
If your dehumidifier keeps turning OFF and ON, then one of the problems could be low amount of refrigerant.
Firstly, you should know that this is not supposed to happen in refrigerant dehumidifiers. They are supposed to keep the same amount of refrigerant in them for life.
The refrigerant during the dehumidifier operation shifts between liquid and gaseous state but never reduces in quantity.
So low quantity of refrigerant in dehumidifier is almost always due to leakage of refrigerant. Poor construction or impact directly to lines could cause leakage in your dehumidifier.
But why does your dehumidifier intermittently turn ON and OFF when it is low on refrigerant?
Actually, leakage of refrigerant causes reduction in pressure in refrigerant lines. Pressure is reduced to the extent that compressor turns off before the completion of cooling cycle.
After sometime when pressure in lines increases, compressor kicks back ON. This working in short incomplete cycles causes high energy usage and may damage your dehumidifier components.
Another indication of leakage is icing on evaporator coils despite adequate room temperature and air flow.
If your dehumidifier is running in short cycles as stated above, diagnose for refrigerant leaks.
It may or may not be difficult to detect leaks. If your dehumidifier got a hit someplace or you notice an unusual bend, it is very likely that there is leak in the same area.
However, this is something that requires experience. So I recommend you call a certified HVAC technician to do this for you. Technician will detect the leak, patch it and recharge for you. It will save you a lot of time and trouble.
Advice: Firstly, check your dehumidifier for other reasons mentioned, that may have caused it to shut off. Rule out the convenient causes, then consider getting your dehumidifier checked for refrigerant loss.
5. Clogged Dehumidifier Coils
When air moves through your dehumidifier, it comes in contact with cooling coils. As a result, its temperature drops below due point and humidity in it is extracted and collects in drain pan.
When I say cooling coils, I refer to evaporator coils. However, air also moves through condenser coils afterwards. Condenser coils restore the temperature of cool air to room temperature.
For proper and consistent dehumidification, air needs to come in contact with the evaporator coils at a sufficient flowrate.
If you have clogged evaporator and condenser coils, air passage will be blocked partially. As a consequence, airflow rate will drop to the extent to cause frosting.
Dust and dirt keep accumulating in coils with time and their cleaning is required from time to time.
Dirty coils will deteriorate quality of air that moves through your dehumidifier. This can have a negative effect on your health. They will also cause the unit to work harder resulting in increased electricity bills and less life of your dehumidifier.
Clean your dehumidifier coils by using a soft brush. Clean them in the direction of tubes. The reason is that these coils are very sensitive and delicate.
In case their geometry is affected, this will cause to reduce efficiency of your dehumidifier or worse may cause a leak and coils will need a replacement.
Accessibility of dehumidifier coils depends upon the manufacturer and model of your unit. Some give easy access to them, while others don’t. If they are not easily accessible and you don’t have enough experience, you can vacuum through the holes above coils.
Best is to expose the dehumidifier coils. Clean debris and dirt carefully, with a suitable brush, in gentle upward and downward motion. Then you could either use a solution like warm water and detergent or dish washer liquid to clean your dehumidifier coils.
However, a really simple product caught my eye the other day. It is specifically built for cleaning coils and able to easily liquefy dirt, oil and grease. It consists of corrosion inhibitors (saves from corrosion unlike water) and has a pleasant smell after application. Give a look at its specification by clicking here.
6. Malfunctioning Dehumidifier Humidistat
Humidistat or humidity control is one of the core components of dehumidifier. It is what decides when your dehumidifier needs to start and when it should stop.
Here is how a humidistat function?
Humidistat continuously detects percentage humidity in the vicinity of dehumidifier. When humidity reaches selected value, it signals the compressor to turn off. When humidity increases sufficiently again, it restarts cooling cycle again by switching ON the compressor.
The electronic humidity sensor is at the inlet of your dehumidifier and it is exposed to adequate flowrate of air. This allows most reliable, accurate and instantaneous measurement of overall humidity in the room.
If your dehumidifier humidistat is faulty, it will measure inaccurate relative humidity level. This will cause your humidity control to shutoff compressor before desired value of humidity is achieved. As a result, you will have incomplete dehumidification.
Pro Tip:One of the most probable indications of a faulty humidistat is that you will have to select somewhat lower value of humidity than required in the controls to achieve the required dehumidification.
Other Reasons for Inaccurate Humidistat Measurement
In case humidistat is measuring incorrect humidity, it is not necessary it is faulty. There are couple of other reasons that could be causing this:
- Humidity sensor is in contact with wet coils.
- Reduced flowrate of air, possibly due to blockage, is causing wrong measurement of humidity. Top reasons for this could be dirty filters or clogged coils.
- Humidity sensor has displaced from default position.
A simple, but not the most convenient and reliable method, for measuring humidity is by an external humidity monitor, for example, hygrometer.
The method in explanation is straight forward. Select required relative humidity in the control panel of your dehumidifier. Humidistat will turn off humidifier at this humidity. Now compare this value with a humidity monitor that serves as a standard for humidity measurement in this comparison.
In theory, the difference of relative humidity between dehumidifier humidistat and the humidity monitor is error in the humidistat of your dehumidifier.
Why Testing Accuracy of Dehumidifier Humidistat Is Not So Simple?
In actual, testing humidistat is far more complicated. So many other factors have to be taken into account before knowing actual error in your humidistat.
I am discussing most important among them below for your knowledge:
Precision and Accuracy of Humidity Monitor
Firstly, precision and accuracy of equipment, which you are considering as standard, has to be taken in account.
All humidity monitors have some error in their measurement. However, as quality increases, accuracy and precision increase, but so does the price.
Exposure to Identical Environmental Condition
Environment chosen, for measurement of humidity, for humidistat and the humidity monitor, must be same.
As the name suggests, relative humidity is actually relative. It changes inversely with temperature. Thereby, for true comparison, both need to be exposed to same temperature and external conditions.
Relation of Time with Humidity Sensor Accuracy
Accuracy of humidity sensors drift with time. With time, error in any humidity measuring instrument will increase and accuracy will decrease.
Just to give you an idea, a humidity meter will drift from its specified accuracy 2-5% per year. So, in three years, humidity sensor could be off by +-6% to +-15% in relative humidity measurement.
Exposure to Sufficient Air Flowrate
You will not get instantaneous and overall value of relative humidity in your room without consistent flow of air.
With humidity sensor at inlet, and consistent airflow through the dehumidifier, you are getting precise room humidity.
However, you have to expose humidity meter to the same sufficient flowrate too. Otherwise, you will get incorrect measurement and comparison will be inappropriate.
Note: Relative humidity is different in different regions of the room. So, both humidistat and humidity monitor, that is set as standard, need to test air in the same region of room.
Pro Tip: Measure with the humidity monitor at the inlet of your dehumidifier. This will allow similar air flowrate and position as the humidity sensor of your dehumidifier.
Identifying error in humidistat is a complex phenomenon. That is why, if your humidistat has not completely failed, I recommend getting it tested from your manufacturer certified technician.
7. Faulty Compressor Unit
The most important component required for your dehumidifier operation is compressor. It is in fact the only necessary moving component in cooling cycle.
Compressor is what pressurizes refrigerant, then heat is taken out from it and it is expanded, before it goes in to cooling coils.
Not very common cause of your dehumidifier short cycling, but a possible one is malfunctioning compressor. If your dehumidifier keeps shutting off after regular small intervals, it could be due to compressor overheating.
If there is a buildup in your dehumidifier compressor that is restricting the flow of refrigerant, it will overheat and shutdown.
Compressor will restart its operation after it cools down sufficiently. However, it will overheat again in no time and turn off.
Due to this, your dehumidifier will operate in short cycles and keep turning off, without achieving desired dehumidification.
Unfortunately, when it comes to compressor malfunctioning, in almost all cases, it cannot be repaired. You will have to replace it entirely. In either case call a certified AC technician to resolve this problem for you.
Advice: Compressor is one of the most expensive components of your dehumidifier. Thereby, before replacement, it is a good idea to compare the price of new compressor with your dehumidifier.
If you ask me, in case your dehumidifier compressor is unrepairable (which most of the time it is), I would suggest you to just buy a new unit. It will save you a lot of trouble and possibly money.
8. Obstructions In Airflow
As I discussed earlier, your dehumidifier needs consistent and sufficient airflow to operate properly. When it is lower than required you will face two problems with it.
First, frosting in the cooling coils. The reason is enough heat not transferred from air to coils. This causes their temperature to go very low.
Second, overheating of the compressor. It has to perform higher magnitude of work to maintain essential airflow.
Both of these problems can cause your dehumidifier to turn Off before completing required operation.
Anything that causes blockage or serves as an obstruction in the path of air through dehumidifier may cause frosting and overheating of compressor.
Keep enough space in the surroundings of your dehumidifier to cause active airflow.
Air from your living space to dehumidifier and vice versa must not be prohibited in any way.
Plants, furniture, decoration pieces or any hindering material should be at sufficient distance from your unit.
9. Problems With Float Switch and Bucket Placement
A dehumidifier collects water from air in your home and stores it in the drain bucket. When the bucket is full, it needs to emptied and reattached again.
When your bucket fills up, internally fitted float switch signals to the dehumidifier control board to interrupt the dehumidifier operation. If this doesn’t happen, quantity of water collected will get higher than the capacity of drain bucket and spill on the floor.
If your float switch is faulty, it will trip and signal dehumidifier compressor and fan/blower to turn off while the bucket is not full.
Diagnosing this problem is usually easy. If your dehumidifier doesn’t turn ON or turns OFF after running for a short while, look for bucket full indicator light.
In case it is indicating that the bucket is full by blinking or is constantly ON, you know that equipment that detects water level is defective. It is restricting the unit to continuously perform dehumidification to complete the process.
Another problem could be improper bucket placement. Actually, when you place drain bucket back in the dehumidifier after emptying or cleaning, there is a push switch that is pressed and your dehumidifier starts working.
The goal of push switch is to ensure proper bucket placement. Without it, if the bucket is not properly fitted, your dehumidifier will keep on running and cause the water to spill on the floor. This is also bad in terms of safety.
If drain bucket is not properly fitted, then loose connection could keep your dehumidifier from turning ON, or working continuously, to carry out required dehumidification. It is also possible that push switch or water container fixture is damaged.
If disturbing the bucket or applying pressure on it slightly causes your dehumidifier to start or stop working then there is a good chance that push switch might be at fault.
If bucket full indicator light is ON, then this is what is prohibiting the operation of your dehumidifier. Take following measures to resolve this:
- Take off the bucket. If it is full, empty it and reattach, your dehumidifier will start running.
- If it is empty and your dehumidifier is indicating a full container, this means there is a problem with float valve. Either it needs adjustment, repairing or replacement.
Second situation is when you diagnose that problem is with the placement of bucket container.
To resolve this, look if something is obstructing proper fixing of the container. If it fixes properly and entirely, then try to apply pressure on push switch, by hand, without bucket. If this turns dehumidifier ON, then that switch needs replacement.
Note: In case push switch is faulty, you will not necessarily know that by using pressure in different directions on it. In case it is electrically failed, you will need to test continuity when it is turned ON.
10. Incorrect Settings in Dehumidifier Control Panel
It is not necessary that your dehumidifier keeps shutting Off because it is defective. There are various options and modes you can select in dehumidifier controls. It is possible that your dehumidifier performs incomplete operation due to the settings you have selected in its control panel.
We have a better sense of temperature in than the humidity. Generally ideal range of relative humidity is from 30-50 percent. It should always be lower than 60 percent.
If you do not have the idea of the relative humidity you want to achieve, it is possible that you have chosen a value close enough to the present humidity conditions, or even above the humidity already present. This causes your dehumidifier to shut down after little operation.
For you dehumidification is not complete but the unit is performing its job the way it is supposed to.
Another reason your dehumidifier runs for a short while is automatic turn Off by timer.
You see when you are running your dehumidifier on timer mode, then it does not matter what humidity you have selected in the humidistat.
Timer will turn Off dehumidifier when selected time duration is complete even if the dehumidification process is not complete.
Give a check to settings in dehumidifier control panel. Make sure timer or any other restricting modes are disabled.
It is not necessary to know the exact value of relative humidity by a hygrometer. Just have an idea of what is relative humidity in your home and desired range as I discussed above. Select this required value to get comfortable atmosphere humidity with less or more but complete operation
Don’t worry if you are overwhelmed by a lot of controls and worried about changes in the settings. You can always reset the dehumidifier to primary default settings.
11. Malfunctioning Electronic Components
Most dehumidifiers are based on vapor compression cycle. In this cooling cycle, basic fundamental operations include compression, condensation, expansion and evaporation.
However, for desired functionality according to our requirements, there are several electronic components that assist components associated with these fundamental processes.
If your dehumidifier keeps turning On and Off, runs in short cycles, or is unable to start, it is possible that one or more of these electronic components are defective or damaged.
Despite humidistat, that I discussed earlier, there are several other electronic components too. Just to have an idea, give a look to purposes and functionalities of these components:
- Capacitor: Stores and releases electrical energy. Dehumidifier generally has two capacitors. One associated with compressor startup and second one creates magnetic flux to rotate the fan/blower.
- Relay: Works as a low power switch to control high power switch. Allows safe switching of dehumidifier components.
- Switch: Controls power and speed of fan
- Control Board: All electronic components link to it. Contains multiple lines with different voltages.
- Fuse: Prevents burning of dehumidifier components due to electrical surges.
There can either be defect in electrical wiring or electronic components.
For example, if your dehumidifier runs for short durations, with incomplete operation, it is usually due to a faulty capacitor. This is because capacitor is a requirement for continuous power to compressor.
In most cases if capacitor is damaged, you will see it bulged on top. It is highly uncertain that despite the bulged body of capacitor it is working fine.
So, how do you detect faults with electrical wiring and electrical components?
Give a look to external and internal electrical wiring and make sure everything looks fine. There should not be any burnt or damaged section. Also check for any loose connections.
Next, you need to check for faults in various components of your dehumidifier. All electronic components (including compressor) connect to control board. Trace current through the circuit. Look for discontinuation in the circuit, especially before and after components.
Remember, different components require different kind of testing. For example, for capacitor, current should slowly reduce from maximum to minimum when testing on multimeter. However, for relay, after it is switched on, before and after is theoretically same. Also check resistors for continuity.
I highly recommend that you check electric components and wiring yourself only if you have experience and familiarity with this subject. Best is to call a certified electrician who will diagnose the fault for you. In case you have a faulty component, replace it with the exact model with same specifications.
These videos below will give you an idea of diagnosis and repair/replacement of these components: