A stuck timer, bad moisture sensor, or blocked vent can keep a dryer running; start with a reset, clean lint, then test sensors and timer.
Why A Dryer Won’t Stop
When a dryer keeps spinning or blowing long past the end of a cycle, the machine isn’t reading “dry” or the control path won’t drop power to the motor. That often traces to a dirty moisture sensor, a stuck timer or control relay, a cycling thermostat that won’t open, a faulty door switch, or a vent that blocks airflow and traps heat. Power surges and software hiccups can also leave the board confused.
Before you grab tools, think safety. Unplug the dryer. If it’s gas, close the gas valve. Pull the unit out for space and better light. Then work methodically from the easy stuff to the parts that need a meter.
Fast Clues And First Checks
| Symptom | Likely Cause | Quick Check |
|---|---|---|
| Runs forever on “Auto” | Dirty moisture sensor | Wipe bars with alcohol; run a small test load |
| Keeps tumbling on “Timed Dry” | Stuck timer or relay | Try a power reset; switch to another setting |
| Heat stops but drum spins | Open heating circuit | Test for heat on Air Fluff vs. heat cycles |
| Blower runs after drum stops | Cool-down feature | Let it finish; see if it shuts off in a few minutes |
| Stops only when door opens | Control not dropping power | Inspect timer, board, or stuck start button |
| Hot cabinet and long cycles | Blocked vent | Detach vent; test with a short cycle |
Dryer Not Turning Off: Common Triggers
Moisture sensor bars. On Auto or Sensor Dry, the drum rides on two small metal bars. Wet laundry creates a tiny signal between them. Wax, softener, and lint coat those bars and the board thinks the load is still wet. Clean both bars with isopropyl alcohol or a fine green pad, then dry with a cloth. Avoid harsh grit that scars the surface.
Timer or control board. In Timed Dry, a mechanical timer or a relay on the board carries power to the motor until the countdown ends. If contacts weld shut or the relay sticks, the motor keeps power. A power reset can release a sticky relay: unplug for five minutes, press and hold Start for ten seconds to bleed stored charge, then reconnect and test.
Cycling thermostat and high-limit cutout. These sensors open and close to hold drum temperature. If one sticks closed, heat may ride high and the cycle logic may never reach its end. If a high-limit trips, heat stops and the timer might stall. Many high-limits reset when cool; some need replacement.
Door switch and start switch. A worn door switch can bounce or stick, confusing the board. A stuck Start button can feed a “run” signal even after the cycle. Each switch should click crisply and show clear open/close on a meter.
Vent path. Lint in the screen, flex hose, wall run, or roof cap chokes airflow. The dryer runs longer, stays hot, and the motor may keep spinning while the board waits for dry readings. Clean the screen every load and clear the vent path on a schedule. The DOE Energy Saver laundry page notes that a clear, rigid vent moves air better and helps avoid heat build-up.
Basic Resets And Safe Tests
1) Power Reset
Unplug the dryer. Wait five minutes. Hold Start ten seconds to drain the board, then reconnect. Try an Air Fluff cycle with a few clean dry towels. If the machine shuts off cleanly, move to a heat cycle and retest.
2) Clean The Sensor Bars
Open the door and find two thin bars inside the drum, close to the lint screen on many models. Wipe with alcohol, then a dry cloth. Run a small load on Auto. If it still runs too long, clean again with a Scotch-Brite pad and repeat the test.
3) Vent Test
Pull the dryer forward. Detach the vent hose. Run a short heat cycle with a light load. If shut-off returns with the hose off, the duct is the bottleneck. Clear elbows, long runs, and the outside cap. The USFA dryer safety flyer urges routine lint removal to cut both run time and fire risk.
4) Timer Check
On a knob-style timer, set 10 minutes of Timed Dry. If the knob never moves or the drum keeps turning past zero, the timer contacts are likely welded. On digital panels, listen for a relay click at start and at stop; a missing stop click hints at a stuck relay.
5) Switches And Thermostats
If the dryer still won’t stop, test the door switch, start switch, cycling thermostat, and high-limit with a multimeter. Each part should show continuity where expected and open when actuated or at rating. Replace parts that don’t match specs from the service sheet inside the cabinet.
What Each Part Does
Knowing the job of each piece makes diagnosis faster. Use the table below as a quick map while you test.
| Part | Job In The Cycle | Failure Sign |
|---|---|---|
| Moisture sensor | Signals “wet” vs. “dry” on Auto | Auto never ends or jumps to cool down too soon |
| Timer/relay | Feeds motor during Timed Dry | Motor runs past zero or won’t start |
| Cycling thermostat | Holds drum heat range | Overheats or never reaches target |
| High-limit | Safety cutout for heat | No heat until cool, or trips again fast |
| Door switch | Stops motor when door opens | Drum keeps turning with door open signal |
| Start switch | Momentary run command | Relay stays latched; motor keeps power |
| Control board | Runs logic, drives relays | Random run-ons, no response to buttons |
Targeted Fixes You Can Do
Clean And Polish The Sensor
Kill power. Remove the lint screen. Reach inside to the bars. Wipe with alcohol, polish with a green pad, wipe again. If fabric softener sheets leave residue, skip them for a few loads and retest. If the dryer now shuts off on Auto, the sensor was the culprit.
Free A Sticky Timer
Mechanical timers can hang after years of arcs across the contacts. A reset may free them. If not, the only stable cure is a new timer. Photograph wire positions before removal.
Swap A Bad Relay
On many boards the motor relay is a cube with spade lugs or solder pins. Look for dark spots or a melted shell. If a relay is soldered, mark and desolder; if it uses lugs, pull straight off. Match voltage and terminal layout when buying a replacement.
Replace A Faulty Thermostat
Cycling thermostats and high-limits sit on the blower housing or heater box. Note the rating stamp. Move one wire at a time to the new part to avoid mix-ups. If a high-limit tripped, fix venting before you run the new part or it may trip again.
Fix Switch Issues
Pop the top or front to reach the door switch. It should click with a firm feel. If the lever is loose or the meter shows no change when pressed, swap it. For stuck Start switches on a panel, pull the knob and inspect the shaft; replace the switch if it binds.
When To Call A Pro
Bring in a licensed technician when the drum won’t stop even with the timer unplugged, when the breaker trips, or when the machine smells hot. Board tracing, shorted harnesses, and motor issues take time and the right tools. If your model is under warranty, start with the maker.
Reduce Run-On Problems For Good
Keep Airflow High
Use rigid metal duct. Keep runs short with gentle bends. Clear the outside cap. Vacuum lint below the screen slot. The Energy Saver page linked above also mentions a cool-down at the end of a cycle; let it finish to carry off heat and protect parts.
Right Loads And Settings
Mix fabrics of similar weight. Spin laundry well in the washer. Pick Auto for mixed loads, Timed Dry for bulky items that shield the bars. Skip “Extra Dry” unless you need it.
Simple Routine
Clean the lint screen every load. Wipe the sensor bars monthly. Pull the dryer and brush the vent twice a year, or quarterly if you dry lots of towels. Don’t run the dryer when you sleep or leave home; stay nearby and listen for odd sounds.
Quick Flow For Troubleshooting
Start with power reset, clean bars, and a vent test. If Auto runs long but Timed Dry stops, suspect the sensor path. If Timed Dry runs past zero, check the timer or a stuck relay. If heat is erratic, watch the cycling thermostat and high-limit. If the motor runs with the door open, inspect the switch or control. Work one branch at a time and you’ll land on the bad piece faster.
Grab the tech sheet stored inside many consoles. It lists test points, wiring colors, and built-in diagnostics. Some models flash codes on the panel; others enter a service mode with a button combo. A basic kit helps: nut drivers, needle-nose pliers, a continuity meter with a buzzer, and a long vent brush. Label wires as you go and take photos. Work slowly, stay organized.
Repair Or Replace?
Compare the age and parts list. A sensor, switch, or thermostat is cheap. A timer or board costs more. If the drum, motor, and heater are sound and the cabinet is solid, a mid-priced repair keeps a good dryer in service. Pair that with a clean vent and fresh seals and you’ll cut cycles and stress on the parts you just replaced.