Why Is My Dryer Not Heating?

Why a dryer needs airflow to make heat

The machine is a loop, and the loop has to keep moving.

The vent, which is most of it

On a vented dryer, work along the whole path. People clean the bit they can see and stop.

• The lint filter, every single load. Not "when it looks full". A film of fabric softener residue also builds on the mesh and blocks it invisibly — if water poured onto the filter sits in a puddle rather than running straight through, wash it in warm soapy water with a brush.
• The filter housing underneath. Lint gets past the filter and packs into the recess it sits in. A vacuum crevice tool reaches it.
• The duct behind the machine. Pull the dryer out and disconnect it. Flexible foil and plastic ducting crushes flat when the machine is pushed back against the wall, and a crushed duct is a total restriction that looks like nothing at all.
• The length and shape of the run. Every bend costs airflow. A duct that snakes around three corners to reach an outside wall will never perform like a short straight one, and the machine will run hot and slow permanently.
• The outside vent hood. The flap should open freely when the dryer runs. Lint packs behind it, and birds and insects nest in it. Go outside with the machine running and feel for a strong warm draught — weak or none means the run is blocked.
• Rigid rather than flexible ducting is worth the change if you are replacing it. Smooth rigid duct carries far more air and catches far less lint than concertina foil.

A quick, telling test: run the dryer with the duct completely disconnected from the back of the machine, venting into the room for a couple of minutes. If it suddenly heats normally, the problem is downstream and you have just proved it — no parts, no engineer. Do not leave it running that way, because it dumps moisture and lint into the room.

The thermal fuse, and why it blew

Nearly every dryer contains a thermal fuse: a small one-shot safety device that permanently breaks the circuit if the machine gets too hot. On many models it kills the heating while leaving the motor running, which produces the exact symptom you are chasing — a drum that turns for a full cycle with no warmth in it at all.

Two things matter here, and the second one is the one people skip.

First, it is a cheap part. Thermal fuses cost very little and are among the more accessible components on many dryers.

Second, it did not fail. It operated. A thermal fuse is not a component that wears out — it is a component that does its job exactly once. It blew because the machine got too hot, and the overwhelmingly common reason for that is restricted airflow. Fit a new fuse without clearing the vent and you will be fitting another one shortly, having learned nothing and having run a hot, lint-packed duct in the meantime.

Related parts on the same thermal circuit, worth knowing by name if you are talking to an engineer:

• The cycling thermostat, which switches the element on and off during normal running to hold temperature. When it fails open you get no heat; when it fails closed you get a machine that overheats.
• The high-limit thermostat, a resettable or non-resettable safety cut-out mounted on the heater housing.
• Some machines have a reset button on the back or inside a panel for a tripped thermal cut-out. Check the manual — it turns a repair into a button press on the models that have one.

Half the power, on an electric dryer

This one is specific to regions where electric dryers run on a two-phase supply, which includes much of North America — and it explains a symptom that otherwise makes no sense.

Such a dryer uses one leg of the supply for the motor and controls, and both legs together for the heating element. Lose one leg and the machine tumbles perfectly, lights up normally, and cannot produce any heat whatsoever.

Causes:

• Half of a double breaker has tripped. A partly tripped double-pole breaker can look closed at a glance. Switching it fully off and then on again is the test.
• One of two cartridge fuses has blown, in older fuse panels.
• A damaged or loose supply cord or terminal block at the back of the machine.

If a dryer suddenly lost all heat while everything else about it stayed completely normal, and especially if that happened around the time of an electrical event in the house, check the breaker before ordering any parts. Where the supply or the terminal block is involved, that is an electrician's job.

On single-phase supplies this particular failure does not arise, and a dead element usually shows up as no heat with everything else normal too — so the distinction matters mainly for knowing whether to check the panel first.

When the element really has failed

Heating elements do fail, generally by going open circuit. What points to it:

• The airflow is demonstrably fine — filter clean, duct clear, strong warm draught outside — and there is still no heat at all.
• It failed abruptly, with no gradual decline in drying performance beforehand. Airflow problems creep up over months; elements tend to stop dead.
• No warmth whatsoever, as opposed to weak or intermittent heat. Intermittent heat points more at a cycling thermostat or a restriction.

An element that has partly failed can also produce a machine that heats weakly, which looks a great deal like an airflow problem. Testing it properly needs a multimeter and access to the heater housing, which is where this stops being a job for most people.

On a gas dryer the equivalent parts are the igniter, the flame sensor and the gas valve coils — and the failure pattern resembles a gas oven's: the igniter glows but the valve never opens, so the drum turns and nothing gets warm. That is a registered engineer's work, not a home repair.

Condenser and heat pump dryers are different

Not every dryer vents to the outside, and if yours does not, several of the checks above simply do not apply.

A condenser dryer recirculates its air, cooling it to drop the moisture into a tank or a drain. Its equivalent blockage points are:

• A full water tank. Most machines stop or refuse to heat when it is full, with an indicator that is easy to miss.
• The condenser unit itself, usually a removable block behind a flap at the bottom front. It clogs with lint and must be rinsed periodically. A blocked condenser is the direct equivalent of a blocked duct.
• The room. Condenser dryers reject heat into the space around them. In a small unventilated cupboard the machine slowly heats its own supply air and performance collapses.

A heat pump dryer deserves its own warning, because it produces a symptom that is routinely mistaken for a fault: it runs much cooler by design. Reach into a heat pump dryer mid-cycle and the clothes feel barely warm, because the whole point of the technology is to dry at low temperature using much less electricity. Cycles are correspondingly longer.

So "my new dryer doesn't get hot" is frequently not a fault at all. The question to ask is not whether it feels hot, but whether the clothes come out dry at the end of a full cycle. If they do, the machine is working as designed. If they do not, check the filters — heat pump machines typically have two or three, including a fine one protecting the evaporator, and a blocked evaporator is the characteristic failure of the type.

Settings that produce a cold cycle on purpose

Free to check, and genuinely common.

• Air fluff, air dry or no-heat. A setting that deliberately tumbles without heat, easily selected by accident and easily missed on a dial.
• A delicate or low-heat programme, which produces so little warmth that people assume the heating has failed.
• The cool-down phase. Every dryer ends its cycle with several minutes of unheated tumbling. Open the door during that window and the machine feels cold — perfectly normally.
• Eco mode, which on some machines lengthens the cycle and lowers the temperature substantially.
• An overloaded drum. Clothes need room to tumble and let air through. A drum packed tight comes out damp with the heating working perfectly, and this is one of the most frequent causes of "it isn't drying" reports.
• Sopping wet clothes going in. If the washing machine failed to spin properly, the dryer is being asked to evaporate several times the usual amount of water and will not finish.

What to check, in order

1. Check the programme. Rule out air-fluff, delicate, eco and the cool-down phase before anything else.
2. Is it a heat pump model? If so, low warmth is normal — judge it by whether clothes are dry at the end.
3. Clean the lint filter, and wash it if water will not pass straight through the mesh.
4. Vacuum the filter housing beneath it.
5. Condenser dryer: empty the tank and pull out and rinse the condenser block.
6. Pull the machine out and check the duct is not crushed behind it.
7. Go outside and feel the vent hood with the dryer running. Weak or no draught means the run is blocked.
8. Run it briefly with the duct disconnected. Heat returning proves the restriction is downstream.
9. Electric dryer, sudden total loss of heat: switch the breaker fully off and on, and check both fuses where applicable.
10. Look for a reset button for the thermal cut-out, if your manual says the machine has one.
11. Still nothing? Thermal fuse, cycling thermostat or element — and clear the airflow before fitting any of them.

Stopping it happening again

• Clean the filter every load. One habit, and it prevents most of what is on this page.
• Wash the filter in warm soapy water every month or two to remove the invisible fabric softener film.
• Clean the full duct run once a year, more often with heavy use or a long run. This is a fire-prevention measure as much as a performance one.
• Use rigid ducting, kept as short and straight as possible, and make sure it is not crushed when the machine is pushed back.
• Check the outside vent flap a couple of times a year for lint, nests and debris.
• Don't overload the drum. Clothes that cannot tumble cannot dry, whatever the element is doing.
• Spin the washing properly first. A faster spin removes water mechanically, which is enormously cheaper than removing it with heat.
• Give a condenser dryer some ventilation. A closed cupboard cripples it.