Your dryer runs. It heats. It tumbles. You come back 45 minutes later and the clothes are still damp. So you run it again.
That second cycle isn't fixing the problem. It's just burning your electricity while the real cause sits untouched.
Here's what's actually going on — and what to do about it.
The Real Split: 90% Venting, 10% Sensor
Most techs who've worked on hundreds of dryers will tell you the same thing: if a dryer heats but under-dries, it's a venting problem nine times out of ten. The remaining ten percent is a failed moisture sensor.
That's it. Two causes. One is a cleaning job. One is a repair.
Let's start with the bigger one.
Why Venting Is Almost Always the Culprit
A dryer works by pushing hot, wet air out of the drum and exhausting it outside. If that airflow is restricted, the hot air backs up. The drum gets humid. Clothes stay wet. The cycle ends anyway because the timer ran out — not because anything was actually dry.
The lint trap catches the visible stuff. But lint doesn't stop at the trap. Fine particles travel past it and slowly coat the inside of the duct that runs from the back of your dryer to the exterior vent cap. Over months and years, that duct narrows. Airflow drops. Drying time doubles.
Check the duct yourself in three steps:
- Pull the dryer away from the wall and disconnect the exhaust hose from the back of the machine. Look inside the hose — if it's packed with lint, that's your answer.
- Check the duct length and bends. Every 90-degree elbow in a flex duct adds resistance equivalent to several feet of straight pipe. A duct with four tight bends may already be pushing the limit before any lint builds up.
- Go outside and find the vent cap. With the dryer running, hold your hand near the opening. You should feel strong, steady airflow. Weak airflow or a cap that barely opens means the duct is restricted.
When to call a vent cleaner vs. a repair tech:
Call a duct cleaning service if the duct itself is intact but clogged. They have rotary brushes and vacuums built for this. It takes about an hour and usually costs less than a repair visit.
Call a repair tech if you've cleaned the duct and the problem persists — or if you see that the duct is crushed, kinked, or improperly routed. Those are installation problems, not cleaning problems.
Also call a tech if the dryer is taking a very long time and running hot to the touch. That combination can point to a thermal fuse that's already failing from years of restricted airflow. The fuse and the vent issue usually need to be addressed together.
The Other 10%: Moisture Sensors
If your venting is clear and the dryer still under-dries, the moisture sensor is the next suspect.
Most modern dryers use two metal sensor bars inside the drum — usually located near the lint trap. As clothes tumble and brush against them, the bars detect electrical resistance. Wet clothes conduct; dry clothes don't. When the sensor reads "dry," the cycle ends.
The problem: sensor bars get coated with residue from dryer sheets. That thin film insulates the bars. The dryer reads "dry" when clothes are still damp and shuts off early.
The fix is simple. Open the dryer, find the two metal bars (they're usually just inside the door, running parallel to each other), and wipe them down with a cotton ball soaked in rubbing alcohol. Let them dry. Run a test load.
If cleaning the sensors doesn't help and venting is confirmed clear, the sensor itself may have failed. That's a parts-and-labor repair — a tech can test it with a multimeter and replace it same day in most cases.
What Not to Do
Don't keep running double cycles and assume it's normal. Dryers that overheat because of blocked airflow are one of the leading causes of residential fires. It's not a quirk — it's a warning.
Don't replace a dryer that just needs a duct cleaning. We see this more than we should. A dryer that heats but under-dries is almost never worn out. It's almost always blocked.
The Honest Summary
Two cycles to dry one load means airflow problem until proven otherwise. Check the duct, check the vent cap, clean the sensor bars. In that order.
If you've done all three and clothes are still coming out damp, that's when a tech needs to look at it. The diagnosis is usually fast. The fix usually follows the same day.