When a dryer still heats but needs two cycles to finish a load, look at the exhaust vent first: lint buildup, a crushed duct behind the machine or a run that's too long are the usual reasons. Clean the lint screen, check for a strong blast of air at the outside hood, and clean the duct. A clogged vent is also a fire risk, so don't put it off.
Why a slow dryer can be a fire risk
A dryer pushes hot, wet air and fine lint out through the vent. When that path narrows, heat builds up inside the cabinet and lint piles up right next to it. A U.S. Fire Administration report on 2008 to 2010 fire department data, as summarized by Fire Engineering, estimated about 2,900 clothes dryer fires in homes each year, with failure to clean as the leading factor (34 percent). It also found these fires were more frequent in fall and winter, peaking in January. An older NFPA fact sheet on dryer and washer fires likewise lists failure to clean as the leading cause, at 29 percent.
On a gas dryer there's a second risk. AppliancePartsPros warns that a clogged vent can force exhaust gases, carbon monoxide included, back into the laundry area, and suggests a CO detector near the laundry space that you test monthly.
1. Rule out the easy stuff first
Confirm the dryer actually heats: run it empty on a heated timed cycle for 5 minutes and feel inside. If it's cold, see our guide on a dryer not heating.
Then look at how you're loading it. Whirlpool suggests filling the drum about half to three-quarters full so clothes can tumble. Air Fluff adds no heat, and Quick Dry is meant for small loads. EcoBoost on some Whirlpool models adds about 40 minutes by design.
Check the washer too. If loads come out of the washer soggy, the dryer is doing the washer's job. Run a Drain & Spin and see whether clothes come out noticeably drier.
2. Clean the lint screen properly
Clear it before every load. If you use dryer sheets, wash it now and then too, since Whirlpool says they can leave residue on the screen. Scrub it with warm water and a soft brush, rinse, and let it dry fully before it goes back in.
Some LG models show F0 if the screen isn't in place. Don't run the dryer without it.
3. Check the airflow at the outside hood
Go outside while the dryer runs on high heat and hold your hand under the vent hood. You should feel a strong, warm stream of air, about like a hair dryer on its high setting, and the flap should be wide open. A weak puff or a flap that barely moves means the vent needs cleaning. The CPSC gives the same advice: if exhaust air isn't escaping outside while the dryer runs, the vent or duct may be blocked.
Clear lint, leaves, nests or snow from around the hood. Whirlpool says the hood must be at least 12 in (30 cm) from the ground or anything else that could block the exhaust, so trim back bushes and keep snow clear of it.
4. Clean the dryer vent safely
Whirlpool recommends cleaning the vent run every one to two years, sooner if drying times creep up or you dry a lot of pet hair. A vent brush kit with flexible rods that chuck into a drill handles most short, straight runs.
Unplug an electric dryer. For a gas dryer, unplug it and leave the gas connector and valve alone. Pull it out only as far as the gas line allows without stretching or bending it.
Loosen the clamp and pull the duct off the dryer's exhaust outlet. Vacuum out the outlet as far in as you can reach.
Feed the brush through the duct from the inside at low speed, turning the direction the kit's instructions give (run it backward and the rod sections can unscrew inside the duct). Work in short sections and pull the lint back out often.
Brush from the outside hood too if you can reach it, and clear the lint that comes out.
Reattach the duct with its clamp, push the dryer back without crushing the duct, and repeat the hand test at the outside hood.
5. Fix bad ductwork
The duct between dryer and wall should be 4 in (10 cm) metal. Whirlpool and the CPSC both say to replace white vinyl or thin foil accordion duct with rigid or semi-rigid metal; Whirlpool notes that foil and plastic can collapse. Keep the run as short and straight as you can, since extra length and every 90-degree elbow cut airflow and let lint build up. Whirlpool notes that many dryers do best with a total equivalent run under 35 ft (10.7 m), but the exact limit depends on your model, so check the installation instructions.
Pushing the dryer back tight against the wall is the other common mistake. Leave enough room behind the machine that the duct keeps its full round shape, with gentle curves rather than folds.
6. Dirty moisture sensor bars
Sensor cycles end when two metal strips inside the drum, usually just below the lint screen, read that the clothes are dry. Softener film on those bars makes the dryer misread the load, and cycles can end early with damp clothes or run long. Unplug the dryer and wipe them with a damp cloth to lift the film. Sears PartsDirect ties Samsung's oD code (excessive dry time) to the moisture sensor bar and its wiring.
Vent warning codes and when to call a pro
Many newer dryers measure airflow and warn you. Whirlpool shows AF or F4E3 (or a Check Vent light), GE shows Check Vent, some GE models show F09 for long dry times, LG shows d80 and its relatives d75, d90 and d95, and Samsung shows Clg after its vent test. Treat these as a fire warning and clean the vent before the next load.
If the duct goes up through a roof, runs a long way inside a wall, or you can't reach both ends, hire a dryer vent cleaning service. Ask them to measure the run and count elbows, and to check the duct for crushed or disconnected sections inside the wall.
When to call a professional
Call a vent cleaning company for runs through a roof or long wall cavities, or if airflow stays weak after you've cleaned what you can reach. If airflow is strong and the dryer still takes too long, book a repair technician to test the heating parts and moisture sensor.
Parts involved
Error codes for this problem
- AF / F4E3Restricted airflow: lint screen or vent blockedWhirlpool
- Check VentLow airflow: the vent is likely blockedGE
- F09 (long dry time)Loads are taking too long to dryGE
- d80Exhaust vent is restricted (Flow Sense)LG
- ClgVent clogged (vent test result)Samsung
- oDDry time too longSamsung
- F0Lint filter not detectedLG
- F3E2Moisture sensor not reading the loadWhirlpool
- HSMoisture (humidity) sensor problemLG
- hEHeating errorSamsung