The short answer
A Bosch WTW-series dryer that ends early with damp clothes, or runs on and on, is usually reporting something about its own airflow rather than about its controls. On a ventless condensing dryer the air is recirculated rather than thrown away, so every restriction in that loop shows up as a cycle that behaves oddly.
What you observe
- The cycle runs far longer than it used to — The machine is not reaching the condition it is waiting for.
- It stops part way and waits — Something has asked it to pause rather than to stop, and on this platform that is usually water.
- The load is warm but no drier — Heat without airflow, which is the classic restricted condensing loop.
- NEAR MISS - the cycle time on the display keeps changing — That is a sensor programme re-estimating as it learns the load, and it is normal on this platform rather than a fault.
Likeliest causes here
- The heat exchanger or condenser block fouled — The second filter in the loop is the one owners never find, and it is the one that decides how well the machine condenses. First, because on these models on this platform this is the part that determines whether a cycle can finish at all.
- The lint filter blinded by a softener film — Lint you can see comes off easily; the invisible film that liquid softener and dryer sheets leave behind is what actually closes the mesh. Second on these models: it is the restriction that never looks like one.
- The moisture sensor bars coated — The bars read the load by conducting through it, and a softener film makes a wet load read dry. Third on this family - wiped clean in a minute with a little vinegar.
- The load size, wet or dry, against the programme — A sensor cycle needs room to tumble; an overloaded drum never presents the sensor with a representative surface. It comes last here - free to test with a half load.
- Where this ranking departs from the brand-generic page — The cause that moves is the heat exchanger or condenser block fouled. It leads on this family because the heat here comes from a refrigerant circuit rather than from an element. That is a property of the platform rather than of the brand, which is why the page above this one cannot rank it the same way.
Check in this order
- Open the lower flap and pull the exchanger out — Rinse it the way the plate on the flap describes and look at what comes off. This is the part that decides whether a cycle can end. It leads on these models because the construction puts it within reach before anything else on the list.
- Hold the lint filter up and run a hot tap through it — Water should pass straight through. Water that beads or pools is a blinded filter and that alone can stall a cycle.
- Wipe the metal sensor bars inside the drum — A little vinegar on a cloth. A filmed sensor reads a wet load as dry, which is exactly the early-finish complaint.
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel or pulling the exchanger - a capacitor can hold a charge after the power is off. Let the machine cool first: the lower compartment stays hot well after a cycle ends. Never run it with the filter out, because that is how lint reaches the parts that are not designed to be cleaned.
When to call
The filter, the sensor bars, the exchanger behind the lower flap, the tank and the load itself are all owner ground on these models, and they account for nearly every cycle complaint. The line is a fault that behaves identically on every programme after all of those are clean: that is a measurement problem, and it needs a meter on the thermistor and the control.
Nearest pages
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
