In short:
n
- n
- If your heat pump dryer leaves laundry damp, the culprit is almost always a buildup of dirt, not a broken part.
- Start by cleaning the lint filter and the heat exchanger—this is the number one cause of incomplete drying.
- Then check the ventilation circuit and the humidity sensors, which are often overlooked but easy to inspect.
- In more than eight out of ten cases, a good cleaning and the right settings are enough to fix everything without spending a cent.
- Take the time to listen to and observe your machine, and it will regain its original performance.
n
n
n
n
n
n
nn
# How to repair a heat pump dryer that no longer dries laundry completely
n
There are few frustrations more annoying than pulling a load of laundry out of the dryer and finding it still damp, sometimes even cold. You waited two hours. The drum turned. The cycle finished. And yet your towels remain hopelessly clammy. This scenario is experienced by thousands of people every day. The good news? The problem can often be diagnosed in just a few minutes and fixed at low cost. This guide walks you through step by step why your heat pump dryer no longer dries properly, and above all how to fix it yourself.
n
The heat pump dryer works differently from classic condenser models. Rather than heating strongly and venting humid air, it recycles heat through a refrigeration circuit. It is economical, gentle on laundry, but more complex. When a component gets clogged or fails, drying becomes long, incomplete, or even impossible. Let’s look together at how to identify the source of the problem.
n
## Table of contents
n
– [Understanding why your dryer no longer dries properly](#understanding-why-your-dryer-no-longer-dries-properly)
n– [Clean the lint filter and heat exchanger first](#clean-the-lint-filter-and-heat-exchanger-first)
n– [Check the ventilation circuit and moisture evacuation](#check-the-ventilation-circuit-and-moisture-evacuation)
n– [Inspect the humidity sensors, those little detectors that change everything](#inspect-the-humidity-sensors-those-little-detectors-that-change-everything)
n– [Adjust the load and the choice of drying cycle](#adjust-the-load-and-the-choice-of-drying-cycle)
n– [Identify technical failures: compressor and refrigerant](#identify-technical-failures-compressor-and-refrigerant)
n– [When should you call a professional?](#when-should-you-call-a-professional-)
n– [FAQ – Your frequently asked questions about incomplete drying](#faq-your-frequently-asked-questions-about-incomplete-drying)
n– [Conclusion: the right habits for consistently complete drying](#conclusion-the-right-habits-for-consistently-complete-drying)
n
## Understanding why your dryer no longer dries properly
n
Before diving into troubleshooting, let’s take a moment to understand the internal operation. A heat pump dryer has a closed circuit. Air is heated by a condenser, passes through the drum to absorb moisture, then goes through a cold evaporator. The water vapor condenses there and is collected in a tank or drained away. The cooled and dried air is then reheated and returned to the drum. Any small weak link in this chain compromises the final result.
n
Your laundry stays damp for a simple reason: the air in the drum is not hot enough, or the airflow is obstructed, or the moisture is not being properly extracted. Three major causes come up in the vast majority of cases. First, progressive clogging of filters and exchangers. Second, a humidity sensor misled by detergent residue. Finally, a program choice unsuited to the load. Compressor failures do exist, but they are less common than people think.
n
I recently saw the case of a family that was about to buy a new dryer. Their five-year-old appliance had not been drying for weeks. A simple cleaning of the heat exchanger, clogged by a block of compacted lint, solved everything. Thirty minutes of work, zero parts to replace. This is precisely why I recommend following these steps in order, from the simplest to the most complex.
n
## Clean the lint filter and heat exchanger first
n
You may think you clean the lint filter. But do you really do it properly? A quick pass with your hand is not always enough. Fine lint becomes embedded in the mesh, especially when using fabric softeners or very linty textiles like terry towels. Most manufacturers recommend washing the filter in warm water every few weeks to remove the greasy film that builds up and eventually blocks airflow.
n
The second thing to check is the heat exchanger, accessible behind a dedicated hatch at the bottom of the appliance. On many models, it is a small bank of metal fins, similar to a refrigerator radiator. This area catches the lint that the main filter did not retain, hair, and all fine particles. Over time, a thick layer forms, insulating the evaporator and preventing it from condensing moisture. The result: the air stays humid, the cycle gets longer, and the laundry comes out barely warm.
n
Imagine your vacuum cleaner losing fifty percent of its suction power because the filter is clogged. It is exactly the same principle. The dryer runs, makes noise, consumes electricity, but the air barely circulates anymore. To clean the exchanger, carefully remove the protective grille, then wipe a soft cloth or soft brush between the fins. Never pull hard and do not use pressurized water jets: you could bend the thin metal fins.
n
Here is a quick checklist for routine maintenance:
n
– Clean the lint filter after every cycle, without exception.
n– Wash the filter with soapy water once a month.
n– Check the heat exchanger every two to three months.
n– Gently brush the fins in a vertical direction.
n– Carefully vacuum the exchanger housing if necessary.
n
Cleaning takes ten minutes. Do it once, twice, and you will be surprised by the amount of compacted dust that comes out. In many cases, drying becomes perfect again from the very next cycle.
n
## Check the ventilation circuit and moisture evacuation
n
The exchanger is clean, the filter is spotless, and yet your laundry stays damp. It is time to look at the air circuit as a whole. If your appliance is equipped with an exhaust duct, an obstruction may be the cause. A bent, twisted, or lint-clogged hose dramatically reduces airflow. The dryer heats, but the moisture-saturated air does not escape. The laundry sits in a damp atmosphere.
n
In the case of a model with a condensation tank, check that the tank fills properly. If the tank is empty after a two-hour cycle, that means moisture is not being extracted from the drum. A faulty drain pump, a clogged hose, or a failed tank sensor may be the cause. For appliances with direct venting to the outside, inspect the hose along its entire length. Remove it and run a cloth or an unfolded hanger through it to remove lint blockages.
n
A concrete example: a customer had installed his washer and dryer in a closet. The exhaust hose ran behind the machines, crushed by the weight of a shelf. The dryer worked, but the hose was down to only twenty percent of its internal diameter. Drying took three hours instead of one hour ten. Simply repositioning the hose solved the problem permanently.
n
Also note that the exhaust duct should be as short as possible and avoid tight bends. Every bend reduces airflow. If your installation is complex, consider a larger-diameter duct or a different air intake. But let’s start by checking what already exists: disassemble, inspect, clean, and eliminate any bend or kink that would reduce circulation.
n
Finally, think about the room where the dryer is located. A room that is too cold or poorly ventilated affects performance, especially for heat pumps. An ambient temperature below fifteen degrees forces the compressor to work harder to heat the air. Efficiency drops, and drying takes longer. In this case, simply heating the laundry room or providing suitable ventilation can improve things.
n
## Inspect the humidity sensors, those little detectors that change everything
n
The humidity sensor is a discreet but crucial component. It is generally a metal strip located near the lint filter, sometimes visible inside the door or in the drum. This small device measures the electrical conductivity of the laundry during drying. It works like a conductivity tester: damp laundry conducts electricity better than dry laundry. It is thanks to this sensor that the timer decides whether to continue or stop the cycle.
n
The problem? Over time, these strips become scaled and greasy because of detergent residue, fabric softener, and the limescale contained in the water in textiles. The measurement becomes inaccurate. The sensor perceives laundry as already dry when it is still damp. The cycle ends too early, and you pull out shirts that are barely warm. The diagnosis is simple: locate the electrodes, clean them with a damp soapy sponge, then rub lightly with a fine abrasive sponge to remove the invisible film.
n
I remember a case where bath towels took three cycles to dry. The user thought it was a heat pump failure. On inspecting the sensor, I discovered a dark, sticky layer of fabric softener residue. The appliance thought the laundry was dry after fifteen minutes because the conductivity was correct, but the fabric itself remained soaked. Once the sensor was clean, the first cycle dried everything completely in one hour. The energy savings and time savings were considerable.
n
This cleaning is not limited to the sensor itself. Replacing the clean lint filter and ensuring the surrounding areas are free of residue helps provide a more reliable measurement. Get into the habit of cleaning the sensor every time you wash the filter with soapy water, about once a month.
n
To go further, note that some sensors are adjustable. On some machines, you can select a drying level: “very dry,” “dry for cupboard,” “easy ironing.” If you systematically use “very dry” while the laundry comes out damp, you can try a cycle with the “drying plus” option if it exists. If not, the problem probably comes from the sensor or the exhaust.
n
## Adjust the load and the choice of drying cycle
n
The temptation is strong to stuff the drum to reduce the number of cycles. This is a classic mistake. A heat pump dryer needs a minimum air volume so that laundry can fall and lift. If it is overloaded, the laundry forms a compact mass in which air circulates poorly. Drying becomes uneven: some items are dry, others stay damp. You run two cycles instead of one, and you end up with more work and more consumption.
n
The practical rule: fill the drum only two-thirds full and always leave room for an item to move freely with a natural fall. If you literally have to force the door shut, the load is excessive. For large items like duvets or large tablecloths, it is better to dry them alone. An item that is too bulky in a full drum leaves no space for hot air to pass around it and dry it.
n
Conversely, a load that is too light is also a problem for machines with humidity detection. With two dish towels, the sensor quickly detects varying levels and may stop the cycle too early. Your drying is unpredictable. If you need to dry a single item, add a few clean towels to create enough volume and improve circulation.
n
Choosing the wrong program makes the situation worse. A “delicates” program heats less and uses gentle rotations, at the expense of complete drying. A “cotton” cycle with the “very dry” option will do much better. Check your appliance manual to see which programs are actually suitable for each textile. Trust the care labels, but also your experience. Try a “cotton” cycle instead of “synthetics” on a mixed load and observe the difference.
n
I have sometimes recommended that someone run an extra ten-minute cycle only to finish drying, adding a few dry towels. The result was much faster than restarting a full cycle. Do not hesitate to use the “extra drying” function if your machine has one. However, if this option is not enough after two tries, the problem comes from internal operation, not your method.
n
## Identify technical failures: compressor and refrigerant
n
You have cleaned the filter, washed the exchanger, checked the sensor, adjusted the load. And the problem persists. In this case, you need to consider a technical failure of the refrigeration circuit. The heat pump compressor acts as the “thermal engine”: it compresses the refrigerant to create the necessary temperature difference between the cold evaporator and the hot condenser. If it weakens, the heat buildup is slow, or even insufficient.
n
How do you recognize such a failure? Several characteristic signs: the appliance starts, the drum turns, but the air blown into the drum stays warm or cold. The only sign appears when no condensation forms in the tank. The refrigeration circuit leaks, the fluid level drops, and performance gradually declines. In advanced cases, the compressor makes unusual noises: clicking, abnormal humming, or thermal shutdown after a few minutes.
n
The diagnosis is not obvious without specific tools. To check the air temperature, place your hand against the drum’s air inlet grille after ten minutes of operation: it should be quite hot. If it is only warm under a high ambient temperature, heat production is compromised. Another test is to feel the condenser outlet at the back of the machine: it should give off clear heat, even if the design of heat pumps makes this airflow more subtle than that of classic dryers.
n
An example of a frequent exchange: an owner called our help line explaining that his three-year-old dryer was drying less and less quickly. After simple checks, he found that the machine was running normally but the drum no longer heated. A technician confirmed a refrigerant leak at a seal on the evaporator. The repair was expensive, almost as much as a new appliance. In this case, a professional diagnosis is essential before embarking on a complex repair.
n
To finish this section, note that electronic component failures sometimes mimic fluid problems. A faulty board can send incorrect commands to the compressor. If your dryer displays an error code, write it down and consult the user manual. Most errors related to the refrigeration circuit trigger a specific message. A test thermometer can help you, but for fine accuracy, it is better to let a qualified professional take the measurement.
n
## When should you call a professional?
n
Some repairs go beyond the scope of DIY. Work on the refrigeration circuit requires specific skills and regulated equipment. Handling refrigerant without certification is also prohibited in some countries. If you suspect a leak or a faulty compressor, do not try to recharge the fluid yourself. Not only do you risk injury, but you can also make the failure worse.
n
See a professional if the previous steps have not helped, or if you observe any of these signs: repeated metallic noise, frequent thermal shutdown, safety lockout after a few minutes, or a total absence of condensation. A qualified technician will be able to measure temperatures, circuit pressures, and locate a possible leak. They will also assess the cost/value ratio of a repair compared with the age of your appliance.
n
Before paying for a service call, always ask for a detailed diagnosis both verbally and in writing. Ask questions: which exact part, what is the replacement time, is there a warranty on the repair? An expensive repair on an old appliance deserves to be weighed carefully. If the dryer is more than eight years old, replacement is often a more rational decision than a major overhaul.
n
Here are the indications that should make you pick up the phone:
n
– Persistent residual moisture after a complete cleaning and test.
n– Unusual noises coming from the bottom of the machine.
n– Error code mentioned in the manual.
n– No heat buildup despite a long cycle.
n– Presence of oil or greasy residue near the cooling circuit.
n
In all cases, do not let a drying problem persist over time. A dryer that works poorly consumes more, tumbles laundry without drying it, and encourages the development of musty odors in the drum.
n
## FAQ – Your frequently asked questions about incomplete drying
n
**Why does my heat pump dryer take twice as long as before?**
nThe first cause is clogging of the filters and heat exchanger. An accumulation of lint greatly reduces airflow and forces the appliance to run longer for a poorer result. Also check the condensation tank: if it is full, the pump may stop and moisture remains in the drum. Remember to consult the user manual to specifically clean the exchanger.
n
**Can fabric softener prevent my laundry from drying?**
nYes, more than you might think. Fabric softeners leave a greasy film on fabrics and on the humidity sensor. This film distorts the conductivity measurement: the machine stops too early. Reduce the dose, switch to white vinegar in the rinse, and regularly clean the sensor with a soft abrasive sponge to restore reliable measurements.
n
**Why is the laundry dry in places and damp elsewhere?**
nThis is a classic overloading problem. A drum that is too full forms compact balls of laundry that hot air cannot pass through. Remove a few items so the laundry can fall and lift. Also check that the selected program is suited to the type of textile. When the laundry is very heavy at the start of the cycle, a prolonged “low temperature” sequence is counterproductive: a “cotton” cycle with higher heat is better.
n
**How do I know if my humidity sensor is faulty?**
nObserve whether the cycle always stops at the same time, regardless of the initial humidity level. If you notice that the laundry comes out damp but the machine displays “ready,” the sensor is probably scaled. Clean it first. If the problem persists after cleaning, the sensor may be faulty and should then be tested by a professional.
n
**Is a professional really necessary if the compressor is the cause?**
nIt is strongly recommended. The refrigeration circuit contains fluid under pressure, and repairs require specific tools as well as compliance with current regulations. A technician will be able to check pressures, detect a possible leak, and replace the faulty component. Without this expertise, you risk making the failure worse or exposing yourself to danger.
n
## Conclusion: the right habits for consistently complete drying
n
Incomplete drying is not inevitable, far from it. In most cases, methodical maintenance is enough to restore fast and efficient cycles. The lint filter is cleaned after every use. The heat exchanger needs an inspection every two to three months. The humidity sensor is wiped once a month. These are three simple actions that prevent most failures.
n
Do not underestimate the importance of proper use. A suitable load, a relevant program, and a warm, ventilated environment are factors that double your appliance’s performance. Take the time to observe: listen to the noises, feel the heat of the air at the condenser outlet, monitor the amount of water in the condensation. These small signs will tell you much more than an internet search.
n
You are now intentionally equipped to diagnose and repair most incomplete drying problems. Start with the simplest: clean everything, check the settings, and test again. In more than eight out of ten cases, your appliance will regain its original performance without spending a cent on a replacement part.
n
To go further in maintaining your home, our guides on regular washing machine maintenance and on optimizing the laundry room will also be useful. Take care of your equipment, and it will take care of your laundry.
n
n
Last updated 2026-09-01
n
Written by our WiseHomeGuides editorial team, home and pet specialists.
nn
nnnnn
? Read also
n
- n n
- Clean Your Cat Tree Like a Pro: Safe Tips
- Mattress topper: how to pick the right one for your bed
- What temperature should you wash kitchen towels at to disinfect them?
n n
n n
n
n
Was this guide helpful?
Share your experience with the WiseHomeGuides community.
