The short answer
A Bosch WQH dryer that runs cold is telling you something about its air path or its supply, not usually about its heater. On the three models listed below the heat source sits downstream of a chain of thermal protection, and that chain is designed to open before anything is damaged. The generic advice to test the element first inverts the order that actually finds the fault here.
What you observe on these models
- Tumbling is normal, heat is absent from the first minute — Nothing has changed except the temperature of the air leaving the drum.
- The problem arrived after the machine was moved — Moves disturb supply connections and ducting, both of which end in this symptom on the three models below.
- One cycle heats and the next does not — Intermittent heat is a connection or a marginal thermal device, not a dead element.
- The panel shows nothing wrong at all — Most no-heat faults on this family are silent, because the control has no way to know heat is missing.
- NEAR MISS - the machine stops mid-cycle and beeps — That is a cycle fault; the no-heat page is only for a cycle that runs to the end.
Causes, most likely first on the WQH family
- A supply problem that leaves the drum turning — First on the WQH family, because it is free to check and it mimics every expensive fault. A machine can have enough supply to run its motor and control and still be missing what the heater needs, and the panel will report nothing. Check this before you buy a part.
- Thermal protection opened by a restriction — Second. The chain of thermostats and cut-outs is the machine protecting itself, and on the three models below it opens quietly: nothing on the panel says it has happened.
- The air path that opened it — Third in rank but always second in the work, because fixing the protection without fixing the restriction guarantees a second failure. Filter, secondary filter or condenser, and the duct if you have one.
- Heater, sensor or control board — Last. Ranked here because everything above it is either free or cheap to eliminate, and because a dead heat source is unmistakable once the three above are clean: no heat, every cycle, without exception.
Check in this order, and why
- First: confirm the breaker and the outlet — Placed first because it costs nothing, takes a minute, and rules out the one failure that perfectly imitates a dead heater on the three models below.
- Second: run a short timed cycle and feel the air — Feel the air leaving the machine, not the drum. Warm air with a wet load is an airflow problem; cold air is a heat problem.
- Third: clear the whole air path — Filter, secondary filter or condenser if fitted, then the duct. Do all of them before running again, so a second test means something.
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. Treat the exhaust path as a fire risk rather than a performance question - lint packed around a heat source is what turns a no-heat call into a fire. If the machine has ever tripped its breaker or smelled hot, stop here and have it looked at rather than running it again to see what happens.
Models in the WQH family
Reference| Model number | Family key |
|---|---|
| WQH235**AU | bosch:dryer:wqh |
| WQH235B8AU | bosch:dryer:wqh |
| WQH235BFAU | bosch:dryer:wqh |
When to call a technician
The line on the three models below is the first fixed panel. Filters, ducting and the breaker are yours; everything from the thermal chain inwards is a service call, because a cut-out replaced without finding what opened it fails again and the second failure is more expensive than the first. Any smell of burning moves this from a repair to a safety call.
Other faults covered for the WQH family
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
