The short answer
A Bosch T-series dryer that tumbles without drying is usually short of airflow rather than short of heat, because a ventless condensing dryer depends on a loop that a restriction closes long before anything electrical fails. this designation spans both condensing architectures, so the end of a cycle decides which one you have: a load that comes out hot was dried by an element, a load that comes out barely warm after a long cycle was dried by a heat pump.
What you observe
- The load is warm but never dries — Heat is present; the moisture has nowhere to go.
- Cycles have been creeping longer for weeks — A restriction building gradually rather than a part failing suddenly.
- The cabinet or the room gets noticeably hot — Heat being dumped where it should not be, which is an airflow story.
- NEAR MISS - the load is dry but only lukewarm to the hand — On a heat-pump machine that is the design rather than a fault: it dries below the temperature an element works at, and a cool dry load is a working machine.
Likeliest causes here
- The lint filter blinded — Lint you can see is not the problem; the softener film you cannot see is, and it closes the mesh to air while looking clean. It leads here, and not by default: it is first because it is free, instant and right more often than anything else.
- A thermal cut-out that has opened — Restrict the air and the machine gets hot where it should not; the cut-out opens and the heat stops, which is the protection working. It sits second on this family because the construction here brings it forward from where a generic list would put it.
- The heat exchanger or condenser block packed — The second stage of the loop collects what gets past the filter, and a packed exchanger stops the machine condensing at all. Third here. An owner job behind the lower flap and the one most often skipped.
- The heating element or its relay — An element that has gone open circuit gives tumbling without heat and nothing else. Last on this family, and deliberately so: straightforward to confirm with a meter and not an owner check.
- Where this ranking departs from the brand-generic page — The cause that moves is the lint filter blinded. It leads on this family because this designation spans both condensing architectures, so the end of a cycle decides which one you have. 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
- Run a hot tap through the lint filter — Water should pass straight through the mesh. Beading water is a blinded filter, and that alone stops a load drying.
- Note whether heat stops part way rather than never starting — Heat that dies mid-cycle is protection tripping, and the restriction that tripped it is the real fault.
- Open the lower flap and clean the exchanger properly — Follow the plate on the flap. This is the single highest-value check on this platform and it needs no tools.
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, and the heating side of a dryer holds more stored energy than most of the cabinet. Let it cool before opening the lower flap.
When to call
The filter, the exchanger behind the lower flap, the tank, the room and the load are owner ground on these models, and on this platform they explain most no-heat calls outright. The line is the heat source: a clean machine that still tumbles cold needs a meter, and that means the cabinet open.
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.
