The short answer
A Bosch WTH-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
- Small loads dry and big ones do not — A marginal airflow problem that only shows when it is asked for everything.
- The cycle ends with the load still damp — The machine believed it was finished. On a sensor programme that is a measurement problem.
- The cycle runs far longer than it used to — The machine is not reaching the condition it is waiting for.
- 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 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. First on this family, and for a reason that belongs to the platform: it is the restriction that never looks like one.
- 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. Second here, and close enough behind the first to be checked in the same pass: on this platform this is the part that determines whether a cycle can finish at all.
- The condensate tank full or its float sticking — A machine that cannot put its water anywhere stops and waits rather than carrying on. Ranked third on these models: the machine usually says so, if there is anywhere on the panel for it to say it.
- The moisture sensor bars coated — The bars read the load by conducting through it, and a softener film makes a wet load read dry. Last, and the ranking is the point: wiped clean in a minute with a little vinegar.
- Where this ranking departs from the brand-generic page — The cause that moves is the lint filter blinded by a softener film. 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
- 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. It leads on these models because the construction puts it within reach before anything else on the list.
- 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.
- Empty the tank, and check the float moves freely — A machine that has nowhere to put its water pauses rather than fails.
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.
