Tumble Dryer Not Heating? Vent, Filter and Condenser Checks
Practical checks for a tumble dryer that runs but will not dry clothes, covering filters, vents, condensers and when a heating fault needs an engineer.
A tumble dryer that spins but leaves clothes damp is frustrating, and it can be a safety matter if airflow is restricted. In many cases the cause is a blocked path for air, which you can clear yourself. Only if those checks fail does it point to a failed heater or sensor.
Safety first
Lint is flammable, and a restricted dryer can overheat. Always unplug before cleaning, never run the machine with the filter missing, and do not leave it running while you are out. If you smell burning, stop and unplug it.
Check these in order
1. Lint filter
Clean the filter after every load. Look for a fine film of lint on the mesh that you can only see by holding it to the light. If water does not pass through it when rinsed, wash it gently with warm water and a soft brush, then let it dry completely.
2. Load size and spin speed
A drum packed too full cannot tumble, and wet washing that came out of a slow spin takes much longer. Check that clothes are properly spun, and dry in sensible loads.
3. Condensate container
On a condenser dryer, empty the water container. A full one can stop the cycle or reduce performance. Make sure it sits properly.
4. Condenser or heat exchanger
Condenser and heat pump dryers have a heat exchanger that collects lint behind the filter or below the door. If it clogs, drying times stretch out. Follow the manual to remove it, rinse it carefully and let it drain. Do not use sharp tools on the fins.
5. Vent hose and outlet (vented dryers)
A vented dryer must push warm air out. Check:
- The hose is not kinked, crushed or too long.
- The outside vent or flap opens freely, and is not blocked by lint, bird nests or insects.
- The hose is straight, short and of the right diameter.
Disconnect the hose and run the dryer briefly. If it dries better, the vent route is the problem.
Environmental factors
A cold garage or unventilated small room can make drying slow, especially for condenser models that need ambient air. Room temperature, humidity and clearance behind the machine all matter. See our running costs guide for why a clean dryer is also cheaper to run.
If the drum turns but there is no heat
| Symptom | Possible cause |
|---|---|
| No heat at all | Heating element or thermal cut-out fault |
| Heats then cuts out | Overheating due to blocked airflow, or a faulty thermostat |
| Dries only part | Sensor or timer fault |
| Takes ages | Blocked condenser, vent or worn seals |
| Hot casing, burning smell | Stop and seek professional help |
Elements, thermostats and thermal fuses can fail with age or after repeated overheating. Fault finding involves mains electricity and should be done by an engineer. Do not bypass safety cut-outs.
Cost and decisions
Heater and thermostat repairs are often moderate in cost, but compare the quote with the machine's age and replacement price using the repair or replace rule of thumb. Check our call-out fee guide to understand how repairs are priced.
To find a local engineer, you can send a request on Compito with details of what you have already checked. Our fault description guide helps you present them clearly.
Preventing it happening again
- Clean the lint filter every cycle.
- Wash the filter with water now and then to remove softener residue.
- Clean the condenser or heat exchanger monthly.
- Keep the vent route short and clear.
- Do not overload.
A worked example
A household finds that a vented dryer, in a utility room, now needs two cycles for a load of towels. The lint filter is clean, so they check the hose behind the machine. It has been squashed by a shelving unit and is full of fluff. Straightening it and clearing the vent flap outside brings the drying time back to normal. A free ten-minute check saved an engineer's visit. Had the vent been clear and the dryer still cold, the heater or thermostat would be next in line.
A timing test
Time a normal load over a few cycles and write down how long it takes to dry. A gradual increase points to a developing blockage or worn seals, while a sudden change suggests a component failure. Telling an engineer "this used to take 80 minutes and now takes over three hours" is a useful clue.
Common mistakes
- Cleaning only the lint filter and ignoring the condenser or vent.
- Forcing a wet filter back in.
- Using an extra-long or tightly coiled vent hose.
- Placing the dryer in a closed cupboard without airflow.
- Resetting a tripped thermal cut-out repeatedly instead of finding the cause.
Edge cases
- Flats: a vented dryer may not have a permitted route outside, so a condenser or heat pump model is often a better fit. Check your lease before drilling.
- Rented homes: report problems to the landlord if the dryer is supplied, and do not alter the venting.
- Garages and outbuildings: cold conditions can slow drying for condenser models.
- Stacked units: washer-dryer stacks have little rear clearance, so check airflow.
When to call a professional
If the machine overheats, smells of burning or trips the electrics, unplug it and leave it until it has been checked. Elements, thermostats and cut-outs involve mains voltage, and safety devices should never be bypassed. If the plug or socket is damaged, a registered electrician should check it.
Frequently asked questions
Why does my dryer run but my clothes stay wet?
Usually airflow. A clogged filter, condenser or vent traps moisture and prevents the dryer reaching proper temperature.
Can a blocked dryer be a fire risk?
Lint is flammable and a restricted dryer can overheat. Keep filters and vents clean and do not ignore burning smells.
How often should I clean the condenser?
Roughly monthly, or more often with heavy use. Check the manual for how to remove it.
Is it worth repairing an old dryer?
It depends on the cost and age. A cheap fix such as a thermostat can be worthwhile, while a major repair on a very old machine may not be.
Can I use a dryer while I am out of the house?
It is safer not to. If something goes wrong, you want to be there to notice a smell or noise and switch it off.