Dryer Takes Two Cycles to Dry: It Is Almost Always Airflow

Drying works by moving heated air through the clothes and carrying moisture out of the house. If it takes two cycles, the air is not moving. This matters beyond the electricity bill: restricted dryer ducts cause thousands of house fires a year.

The test that tells you immediately

Run the dryer and go outside to the vent hood. You should feel a strong, warm airflow — enough to hold a hand against and feel pushed.

If the airflow is weak, you have a restriction and the rest of this article applies. If it is strong and clothes still do not dry, then look at the heating element or thermostats.

Where the restriction is

Work from the machine outward.

1. The lint filter. Clean it every load. Then check something people miss: if you use dryer sheets, a film builds up on the mesh that air will not pass. Run water through the screen — if it pools rather than flowing straight through, scrub it with warm soapy water and a brush.

2. The filter housing. Lint gets past the screen and packs into the duct below it. A vacuum crevice tool, or a dedicated dryer lint brush, reaches it.

3. The transition hose behind the machine. Two problems here:

• Crushed. Pushing the dryer back against the wall kinks the hose. This is extremely common and instantly halves the airflow.
• Wrong material. Foil or plastic flexible duct traps lint in its ridges and is a fire hazard. Use rigid or semi-rigid metal duct. Plastic flexible duct is prohibited by code in most places.

4. The duct run itself. Every elbow costs airflow, equivalent to several feet of straight run. Most manufacturers cap the total at around 25 feet of equivalent length. A long run with four elbows is over budget before you start.

5. The exterior vent hood. Check the flap opens freely. Birds nest in these, and lint packs the louvres solid. A hood with a fine mesh screen will block completely — remove the screen.

Cleaning the duct

Disconnect at both ends and pull it through with a duct brush kit on a drill, or a shop vacuum from the outside end. Do this annually; twice a year for a long run or a large household.

While it is apart, seal joints with foil tape, not duct tape. Duct tape adhesive fails in heat, which is a mild irony.

If airflow is genuinely fine

Then look at heat:

Electric dryers — the heating element, the high-limit thermostat, and the thermal fuse. A thermal fuse blows because of overheating, which is nearly always caused by the airflow restriction above. Replacing a blown fuse without clearing the restriction means blowing another one.

Gas dryers — the igniter, the flame sensor, and the gas valve coils. If the drum turns and you hear the igniter click without a burn, that is a coil or valve problem.

Both — a failed moisture sensor makes an auto-dry cycle stop early. Test by running a timed cycle instead. If timed drying works and auto does not, it is the sensor. On many dryers the sensor is two metal strips in the lint filter housing; they sometimes just need wiping clean of fabric softener residue.

Load habits that matter

• Do not overload. Clothes need to tumble to expose surfaces.
• Spin them properly first. A washer that leaves clothes soaked doubles the dryer’s work; if your washer spin is weak, fix that instead.
• Do not run one item alone — it plasters itself to the drum and never dries.

The fire point, stated plainly

Lint is highly combustible, and a restricted duct traps hot lint against a heat source. The warning signs are clothes hot to the touch at cycle end, a burning smell, and the outside of the machine running hot. If you see those, stop using it until the duct is clear.

Duct sizing, properly

Manufacturers specify a maximum equivalent length, and every fitting counts against it. Typical allowance is 25 feet total for a 4-inch rigid duct, reduced by:

Fitting	Equivalent length
90-degree elbow (rigid)	5 ft
45-degree elbow	2.5 ft
Flexible transition hose	5 ft per foot used
Louvred vent hood	0–5 ft depending on design

So a run with three 90-degree elbows has spent 15 of its 25 feet before any straight pipe. A four-foot flexible hose behind the machine can consume the whole budget on its own.

If you are over budget, options are a shorter route, fewer elbows, an upgrade to larger-diameter duct where the manufacturer permits it, or a booster fan specifically listed for dryer use.

Rigid, semi-rigid, or flexible

• Rigid galvanised or aluminium duct — smooth bore, minimum resistance, minimum lint retention. Use it for everything except the last connection.
• Semi-rigid aluminium — acceptable for the short transition behind the machine where a bend is needed.
• Foil flexible — permitted in some jurisdictions for short transitions only. Its ridges trap lint.
• White vinyl or plastic flexible — prohibited by code in most places and a genuine fire hazard. If your dryer has this, replacing it is the single highest-value thing on this page.

Join sections with the male end pointing in the direction of airflow, so lint does not catch on the joint. Seal with foil tape, and use no screws that protrude into the duct — a screw tip in the airstream collects lint until it blocks.

Vent hoods

The hood is where restrictions concentrate, because it is the part exposed to weather and wildlife.

• A damper flap that swings freely is what you want.
• A fine mesh screen will block solid within months. Remove it. If pests are the concern, use a hood designed with a pest guard that does not obstruct airflow.
• Louvred multi-flap hoods restrict more than a single damper.
• A hood discharging into a soffit or an attic is wrong regardless of condition. Moisture belongs outside the building envelope.

Check it on a windy day too: a hood that chatters or blows open is fine, but one that is held shut by wind pressure on the wrong elevation will cause complaints you would otherwise blame on the machine.

Gas dryers and combustion

A restricted duct on a gas dryer has an additional consequence: the burner needs adequate airflow to burn cleanly, and a starved burner produces carbon monoxide.

The dryer must also have combustion air available in the room. A dryer in a small sealed cupboard with a bathroom extractor running can be pulled into a negative pressure situation, which is exactly how flue gases end up indoors.

Fit a CO alarm in the vicinity if there is not one already.

Efficiency, since it is the reason people notice

A restricted dryer uses roughly double the energy per load and takes double the time. On a household doing five loads a week, clearing the duct pays for the brush kit in a couple of months and then keeps paying.

Two other habits with real effect: clean the lint filter every load, and use the moisture-sensing auto cycle rather than a timed one so the machine stops when the clothes are dry rather than running to a clock.