The short answer
A dryer that ends a cycle early is nearly always protecting itself from a restricted vent. The duct through the wall is the part nobody inspects, and it is where this fault lives far more often than any sensor or board.
What you actually see and hear
- Cycles end early with the load still damp — Sensor drying acting on a restriction, a small load or coated sensor bars.
- It stops part-way and restarts only after cooling — A thermal cut-out operating because air is not moving.
- It takes two or three cycles to dry a normal load — Gradual airflow loss, almost always lint in the duct.
- The laundry room gets hot and humid during a cycle — Air is escaping into the room rather than outside - a disconnected or split duct.
- NEAR MISS - it runs the full time with no heat at all — That is a heating fault, not a cycle fault.
Causes, most likely first on this machine
- Restricted vent duct or a blocked outside flap — First and by a wide margin. A long duct silts up over years, and a flap stuck shut by lint, paint or a bird's nest stops the air completely.
- Lint filter partly blocked — Second. A washed filter is clean; a shaken one is not, and dryer-sheet residue forms an invisible film.
- Small loads and sensor drying — Third. Sensor bars need damp fabric touching them, and a couple of items never give a reliable reading.
- Sensor bars coated with softener residue — Fourth. The film insulates them and the machine reads dry from the start.
- Thermostat or thermal cut-out — Fifth, and usually a consequence of the causes above rather than a fault in itself.
- Control board — Last, and it is what remains after everything upstream is clean.
Check in this order, and why
- Clean the lint filter, then look down the duct — Airflow is behind most of the ranking and it costs nothing to check.
- Go outside and watch the flap while the dryer runs — A flap that does not open is a complete diagnosis.
- Run a timed cycle instead of a sensor cycle — If timed drying works, the fault is in what the machine senses.
- Wipe the sensor bars and try a full load — Two checks that clear the middle of the list.
What an owner can safely check
- Wash the lint filter in warm water and dry it fully — A film you cannot see restricts air enough to end a cycle early.
Tools: warm waterAbout 10 min
- Watch the outside flap open while the dryer runs — If it does not open, nothing else matters until it does.
About 10 min
- Disconnect and clean the duct along its whole length — This is the job that fixes most of these faults, and it is overdue on most installations.
Tools: duct brush, vacuumAbout 60 min
- Wipe the sensor bars inside the drum with a little vinegar — Removes the softener film that makes a wet load read dry.
Tools: cloth, white vinegarAbout 10 min
- Run a timed cycle with a full load and compare — It tells you which half of the machine is at fault.
About 60 min
- STOP HERE before testing thermostats or the control — Live work behind a panel on a high-current appliance.
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel - a capacitor can hold a charge after the power is off. A full-size dryer is on a dedicated large-appliance circuit, so switch off at the breaker rather than at any switch, and treat the terminal block as live until you have. Lint is fuel: never run the machine with the vent disconnected indoors, and never bypass a thermal cut-out to get a cycle to finish.
When to call a technician
Call when a timed cycle dries normally, the duct is clean end to end, the flap opens and sensor cycles still end early - that is a sensor or control fault. Call promptly if the machine keeps stopping on a thermal cut-out, because repeated tripping means heat is building where it should not and lint is fuel. If the duct has never been cleaned, do that before booking anything: it is the cause far more often than any part.
Nearest pages of this class
What this page does not cover
This page is written for the full-size vented dryer class, not for one family or model line. Where a brand- or model-specific page exists for your unit it is the more specific answer and it is linked above, so go there first if your machine is named. What is deliberately not here: drum roller, belt and idler part numbers, thermostat ratings, element specifications and vent length limits, all of which differ by family and belong on the page for that family.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
