The short answer
On a Bosch dryer, the first thing to check is a restricted vent or lint-blocked exhaust run. A dryer that turns but never gets hot is usually being protected rather than broken: something has cut the heat because airflow fell, or half the supply has gone. Bosch dryers are compact European machines with a condenser path rather than a long rigid vent, so heat complaints on this platform are usually about the condenser and the lint stack, not about the duct behind the wall. Clear the vent first - it is upstream of most of the parts people replace.
What you observe
- The drum turns and the load comes out cold — Motor and control are fine, which puts the fault in the heat circuit or its protection.
- The cycle runs its full time and stops — A timed cycle completing with cold clothes points away from the control and toward the heat.
- The outside vent hood barely moves — Weak exhaust at the hood is the single most useful observation on this complaint.
- NEAR MISS - it heats but clothes are still damp — Heat that is present but ineffective is an airflow or cycle-sensing complaint and belongs on a different page.
Causes, most likely first on Bosch
- A restricted vent or lint-blocked exhaust run — Lint builds along the duct until airflow falls, the machine overheats, and the protective devices cut the heat. Ranked first because it is upstream of every protective device in the machine, so it causes the fault that looks like a part failure. On Bosch, the condenser path replaces the long rigid vent, so the lint stack inside the cabinet is where restriction builds.
- A thermal fuse or high-limit thermostat that has opened — These are one-shot and self-resetting protectors on the heater circuit. Ranked second because it is the part that acts when airflow falls, so it is the commonest thing actually found open.
- An air-fluff or no-heat setting selected — Air-fluff, delicate and some sanitise or timed settings run the drum with little or no heat by design, and a knob knocked one position is easy to miss. Ranked third because it costs nothing to eliminate and it accounts for a share of these calls every year.
Check in this order, and why
- Run the dryer and feel the exhaust at the outside hood — Strong warm airflow at the hood clears the vent; a weak trickle is your answer. It comes first because the ranking above puts a restricted vent or lint-blocked exhaust run ahead of everything else on this platform.
- Note whether the drum still turns with no heat at all — Tumble with zero heat is the classic pattern for an open protector on most platforms.
- Select the plainest timed heated cycle and start again — It removes the whole class of setting errors in one test.
What an owner can safely check
- Clean the lint filter, the filter housing and the vent duct — Pull the filter and wash it, vacuum the housing below it, then disconnect the duct at the back and clear it along its whole length to the outside hood.
Tools: vacuum, vent brushAbout 45 min
- Reset the breaker fully and re-test on a heated cycle — Switch the dryer breaker completely off, hold it there, then switch it back on, and run a heated cycle rather than an air-fluff one.
About 10 min
- STOP HERE if the next check needs a meter on live terminals — Everything past this point is measured with power applied, and that is where an owner check ends and a service call begins.
Before you open anything
Safety
Unplug the dryer or switch off its breaker before removing any panel - a capacitor can hold a charge after the power is off. If this is a gas dryer and you smell gas, do not switch anything on or off: leave the building and call the gas utility or emergency services from outside. Never run a dryer with the vent disconnected into the room, and never use plastic or vinyl duct: lint plus heat in a flexible plastic duct is how dryer fires start.
When to call a technician
Call once the vent is proven clear, the breaker has been fully reset and the machine still tumbles cold, because the next checks are continuity tests on the heater circuit with the panel off. Call a gas technician rather than testing anything yourself if this is a gas dryer that is not lighting, and call immediately if you smell gas or see scorching at the terminal block.
Nearest pages of this class
What this page does not cover
This page covers the Bosch dryer as a class, not one family or one model line. What changes from build to build - wiring colours, part numbers and component test values - is deliberately absent. Where your model plate names a line, use that line's documentation first.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
