Has your dehumidifier stopped working? Or is it extracting less water than you had hoped?
The best modern dehumidifiers are durable and long-lasting machines. But any electronic device can develop faults – and dehumidifiers are no exception.
In this article, we’ll go through the most common reasons for a dehumidifier to stop working. We’ve also included some tips for solving basic problems.
Disclaimer: Always read the manual and contact the manufacturer if you suspect a fault. Trying to do your own repairs could invalidate the warranty. DIY repairs may also be dangerous, especially as dehumidifiers are run for long periods without supervision.
A Quick Overview of the Two Types of Dehumidifier
Before you can start troubleshooting, you need to check which type of dehumidifier you own.
Refrigerant (or compressor) dehumidifiers are the most common in the UK. They are noisy machines, but do a great job at extracting water with minimal energy usage – particularly in warmer conditions. Refrigerant models rely on passing warm air over cooler coils so water condenses and drips into the tank.
Desiccant dehumidifiers are less energy efficient, but are better in cooler conditions. This makes them a popular choice for garages or unheated rooms. They are also smaller and quieter than refrigerant models.
The compressor is one of the most likely components to develop a fault. If it stops working, the machine can’t extract water until professionally repaired. Desiccant machines don’t have a compressor, which is one less thing to go wrong.
Keep this in mind as you read the rest of the post, as any mention of a compressor can be ignored if you own a desiccant model.
Note: There are also peltier dehumidifiers. These are less effective at extracting water, so we usually don’t recommend them.
Common Reasons a Dehumidifier Isn’t Collecting Much Water as You Expect
If your dehumidifier has stopped working – or at least stopped removing as much water as it once did – there may not be a mechanical or electric fault. Instead, it could be due to a change in external conditions.
Low Temperatures (Compressor/Refrigerant)
Refrigerant dehumidifiers need a temperature difference between the air and coils. When warmer air hits the cooler coils, moisture condenses and falls into the tank. As the external temperature drops, the coils must become cooler to maintain a temperature difference.
The result is that refrigerant dehumidifiers become less effective as the temperature drops. If your machine is still working, but doesn’t remove as much moisture as it once did, a lower temperature could be the problem.
At a certain temperature the coils may also start to freeze. Modern dehumidifiers have an automatic de-freeze function, but the machine can’t extract water when this process is running.
Large Extraction Capacities
Dehumidifiers with high maximum extraction rates are designed to dehumidify entire homes. If you use them in a small room, they are likely to bring the humidity down quickly, which means they won’t extract much water.
This isn’t a problem – there’s no need to run the dehumidifier if the relative humidity has reached your target levels. But it can make it seem like the dehumidifier isn’t working, when it’s actually just done its job quicker than you thought.
All dehumidifiers will also remove more moisture during the first week of operation. Once humidity levels have been reduced to a manageable level, there is less water to remove.
Dehumidifiers are listed with a maximum extraction capacity. This is the theoretical amount of water the machine could remove in ideal conditions.
The key words here are “ideal conditions.” For refrigerant dehumidifiers, these conditions are 30 degrees Celsius and high levels of humidity (~80%).
You’re unlikely to ever have these conditions in the average UK home. So, if you expect a dehumidifier with a 20 litres per day capacity to extract anywhere close to this amount, you’ll be disappointed.
Potential Faults That Can Caused a Dehumidifier to Stop Working
If you’ve ruled out external reasons for your dehumidifier to stop working, the machine may have a faulty component.
You should always contact the manufacturer if you think your dehumidifier has developed a fault. Even if your machine isn’t under warranty, the manufacturer’s support team is the best source for how to repair your make and model.
With that said, here are some of the most common dehumidifier faults.
Blocked Filter or Restricted Fan
Dehumidifiers blow air over internal coils to remove air and prevent ice build-up. If there isn’t enough airflow through the machine, the dehumidifier will struggle to extract moisture.
This is a relatively easy problem to identify. Put your hand near the grill and check how much warm air is blowing out of the dehumidifier. If the airflow is weak, this can cause the dehumidifier to struggle.
Start by checking the filter for potential blockages. If the filter is clogged with dirt or fluff, remove it so air can flow freely. Filters should be cleaned regularly so the dehumidifier doesn’t become less efficient over time.
Next, check the fan hasn’t become caught or blocked. It should be able to spin without restriction to maintain the correct airflow.
If you’re not a trained electrician, don’t test the fan with the machine plugged in. Instead, contact a professional who is comfortable working with a live dehumidifier.
Blocked Drainage Hose
Nearly all dehumidifiers have a continuous drainage option. This allows water to run away via an external pipe into a drain or sink, rather than filling up the machine’s water tank.
While continuous drainage can be a useful feature, it relies on gravity for water to be removed from the machine. If there is a kink or other blockage in the hose, the water won’t flow and the dehumidifier will stop working.
Leaking Refrigerant Fluid
Refrigerant fluid is essential for a dehumidifier to extract water from the air. While the refrigerant should be in a closed system so it doesn’t run out, the reality is that small leaks can sometimes develop.
You should be able to spot a leak by checking inside the dehumidifier (make sure the power is off). If you can see the refrigerant has been leaking, or there appears to be other damage within the machine, contact a service professional.
Of course, this won’t be an issue if you have a desiccant dehumidifier.
Refrigerant dehumidifiers rely on a compressor to extract water from the air. The compressor pumps refrigerant through the machine and into the evaporator, where it’s used to extract water. If this vital part develops a fault, the machine won’t be able collect moisture.
The most common sign of a faulty compressor is an intermittent buzzing. This is often caused by a problem with the capacitor in the compressor, but can also be the result of a failed overload device.
Unfortunately, you’ll either need to replace the machine or contact a professional for repair.
Faulty Humidistat or PCB
Most dehumidifiers have a built in humidistat for measuring the relative humidity. If this is faulty, the machine will receive incorrect information about the current humidity.
It might, for example, think humidity has reached your target level, when it’s actually much higher. This can cause the dehumidifier to stop working, despite there being nothing wrong it.
The most common cause of this issue is a faulty electronic control board. Again, this issue must be tested and fixed by a professional.
If your dehumidifier has stopped working, however, the first step is to work out why it’s extracting less water. Has the machine developed a fault? Or is there an external factor causing reduced extraction rates, such as lower temperatures or dry air?
Always contact the manufacturer if you suspect there is a fault in the machine. Dehumidifiers are electronic devices that run for long periods, so it could be dangerous to try and complete your own repairs.
Has your dehumidifier developed a fault or other issue? Tell us about it in the comments below.