Why Is My Tumble Dryer Not Heating Up?
Most cold tumble dryers come down to trapped heat and blocked airflow so start with the simple checks before calling anyone out.
The short answer
The most common reason a tumble dryer stops heating up is that it has overheated and tripped its heater cut-out, and the trigger is almost always restricted airflow from a clogged lint filter or a blocked exhaust vent hose. Unplug the dryer, clean the filters, clear the hose, then press the reset button on the back. If it trips again, the thermostat or heating element needs replacing.
A dryer that tumbles away for an hour and hands you back a drum of damp, cold washing is one of the more annoying faults in the house, but it's rarely a big one. The cause is normally something simple, and most of the checks below need nothing more than a screwdriver and the machine pulled out from the wall.
Some newer machines will flash an error code when the heater stops working. Those codes point you in the right direction, but they don't always name the real cause, and plenty of basic dryers have no display at all. That leaves you to work through the likely faults yourself, starting with the easiest.
Before You Start Checking Your Dryer
Switch the dryer off and pull the plug out of the socket before you touch anything at the back. The heater and its wiring sit behind the rear panel, and you don't want power anywhere near your hands while that panel is off. Give the machine time to cool down too, as the element and the metal ducting around it stay hot for a while after a cycle.
It's also worth knowing which kind of machine you've got. A vented dryer pushes warm, damp air out through a hose, while condenser and heat pump models collect the water in a tank and have a condenser unit to keep clean instead. Our guide to the different types of tumble dryer explains how each one works. The photos in this guide show a vented machine.
Why Is My Tumble Dryer Not Heating Up?
Work through these four faults in order. The first three are quick and free to fix, so it's worth ruling them out before you start buying parts.
1. The Heater Cut-Out Has Tripped
The most common reason a dryer runs cold is that its overheat protection has done its job. When the heater gets too hot, a thermal cut-out breaks the power to the element so the drum keeps turning but no heat comes through. On many machines this cut-out has a small reset button on the back, which is sometimes a red button you can reach straight away and sometimes tucked behind the rear casing.
If yours is behind the casing, undo the screws around the panel and lift it away to get at the heater housing. Press the reset button firmly, refit the panel and run a short cycle. If the dryer heats up and then trips again, something is making it overheat, so carry on with the checks below rather than resetting it over and over. Some machines use a one-off thermal fuse with no reset button, and that part has to be replaced once it's blown.
2. The Door And Lint Filters Are Clogged
Every dryer relies on air moving freely through the drum, over the heater and out again. The lint filter catches the fluff that comes off your clothes, and once it's coated the air can't get through, so heat builds up around the element until the cut-out trips. A clogged filter also means longer drying times, which is the first sign most people notice.
Clean the lint filter after every load. It takes seconds, as the filter simply lifts out of the door opening, opens up, and the fluff peels off by hand. Give the filter a rinse under the tap now and then if fabric conditioner has left a film on the mesh, and let it dry fully before it goes back in.
3. The Exhaust Vent Hose Is Blocked
On a vented dryer, the hot, damp air has to leave through the exhaust hose. If that hose is kinked, squashed behind the machine or lined with lint, the air backs up and the heater overheats in exactly the same way as it does with a clogged filter. A blocked hose also lets steam and fluff escape into the room, so a utility room that turns humid while the dryer is on, or clothes that come out covered in lint, are both clues.
Unclip the hose from the back of the dryer and look straight through it. Pull out any lint with your hand or a vacuum nozzle, check that it runs to the outside vent without sharp bends, and make sure it's pushed firmly back onto the outlet. If the hose goes through a wall, check the outside flap opens freely too. Our guide to installing a vented tumble dryer shows how the hose should be routed.
4. A Thermostat Has Failed
If the filters and hose are clear and the cut-out keeps tripping, or the dryer won't heat at all after a reset, a thermostat is the likely suspect. Most dryers have two near the heating element at the back of the machine. One controls the drying temperature during normal running, and the other is a safety thermostat that steps in if the first one fails.
To replace them, remove the rear casing as you did for the reset button, take a photo of the wiring so you know where each connector goes, then pull the wires off and unscrew the old thermostats. Fit the new ones and reconnect the wiring exactly as it was. Thermostats are cheap parts and worth changing on an older machine, but if you're not happy working on appliance wiring, this is the point to call an engineer.
Keeping Your Tumble Dryer Heating Properly
Almost every fault in this guide starts with air that can't get out of the machine, so a few minutes of care here and there saves most of the hassle. These habits keep the air moving:
- Empty the lint filter after every load and check the door seal area for loose fluff.
- Look at the exhaust hose once a month and clear any lint build-up before it narrows the airflow.
- Keep the hose as short and straight as you can, with no loops or squashed sections behind the machine.
- On condenser and heat pump models, empty the water tank and clean the condenser unit as the manual recommends.
- Leave a gap behind the dryer so warm air around the casing has somewhere to go.
A vented dryer that can't push its moisture outside fills the room with damp air instead, and that soon shows up as condensation on windows and black spots in corners. If you've already got that problem, our guide on how to get rid of mould covers the clean-up, and a dehumidifier for damp utility rooms helps keep it from coming back.
When To Call An Engineer Or Replace The Dryer
If you've cleaned the filters, cleared the hose, reset the cut-out and the dryer still runs cold, the heating element itself is the next suspect. Elements can be tested with a multimeter and swapped, but it's a bigger job than a thermostat and involves more of the machine coming apart.
Call an engineer if you smell burning, see scorch marks on the heater housing or the cut-out trips on every single cycle even with clear airflow. On an older machine, weigh the cost of the call-out and parts against a new dryer, especially if it's had other faults. Our guide to the types of tumble dryer and their running costs is a good starting point if you decide to replace it.
Other Questions We Get Asked
Where is the reset button on a tumble dryer?
The reset button on a tumble dryer sits on the back of the machine, near the heating element. On some models it's a small red button you can press straight away, while on others it sits behind the rear panel and you'll need to undo a few screws to reach it. Unplug the dryer and let it cool before pressing it.
Why does my tumble dryer keep tripping the heater?
A tumble dryer that keeps tripping its heater cut-out is overheating, and blocked airflow is the most common cause. A clogged lint filter, a kinked or lint-filled exhaust hose or a stuck outside vent flap all trap hot air inside the machine. If the airflow is clear and it still trips, a faulty thermostat is the next thing to check.
Is it worth repairing a tumble dryer that won't heat?
Repairing a tumble dryer that won't heat is worth it when the fault is a blocked filter, a blocked hose or a thermostat, as those cost little or nothing to fix. A failed heating element on an older machine is a closer call, so compare the cost of the part and any call-out against buying a replacement dryer.
Can a blocked vent hose stop a tumble dryer heating?
Yes, a blocked vent hose can stop a tumble dryer heating. When the hot, damp air can't escape, heat builds up around the element until the thermal cut-out trips and switches the heater off. The drum keeps turning, so the dryer seems to work but blows cold air. Clearing the hose and resetting the cut-out normally fixes it.
Does the lint filter need cleaning after every load?
Yes, every load. A coated filter starves the dryer of airflow until it overheats and trips its heater, and clearing it only takes a few seconds of peeling fluff off by hand. Now and then, rinse the mesh under the tap to shift any film left by fabric conditioner, then let it dry fully before it goes back in.
Is it safe to keep pressing the reset button when the dryer trips again?
No, resetting the cut-out over and over only hides the problem. A dryer that trips a second time is still overheating for a reason, and the lint filter and exhaust hose are where to look before you press that button again. Some machines use a one-off thermal fuse with no reset button, and that part has to be replaced once it's blown.
Can I replace the thermostats on a tumble dryer myself?
Yes, as long as you're comfortable working on appliance wiring. The parts are cheap and the job is mostly about keeping track of the connectors, so unplug the dryer, take off the rear casing and photograph the wiring before you pull anything off. Then swap the old thermostats for new ones and reconnect everything exactly as it was. If wiring isn't for you, call an engineer.
When is it time to call an engineer about a dryer that won't heat?
Any smell of burning or scorch marks on the heater housing means calling an engineer straight away, and so does a cut-out that trips on every cycle with the airflow clear. A dryer that still runs cold after clean filters, a clear hose and a reset points to the heating element, which is a bigger strip-down than most people want to tackle.
Richard has spent years renovating properties and turning them into rentals and Airbnbs. Like a lot of people he started out as a beginner, and these days there isn't much DIY he won't take on.