The short answer
On the T models, no heat with a turning drum has three candidates in a fixed order: restricted airflow, a tripped safety device, and the heat source itself. The table below carries two model codes for this family, close enough in build that the layout described here holds across both.
What you observe on these models
- The drum turns normally and the load comes out cold and damp — The heat is not being produced or not being allowed. The drum motor is fine, so that is half the machine already ruled out.
- The cycle runs its full time and the clothes are barely warm — Partial heat, which on an electric machine often means one leg of the supply is missing: the drum turns on one leg while the element needs both.
- It heated yesterday and does not today, with no other change — A safety device has opened. Something restricted the air and the machine protected itself, and the restriction is still there.
- There is a scorched smell with the cold load — Stop the machine and leave it off. A scorched smell with no heat points at lint that has been overheated, and that is a fire risk.
Causes, most likely first on the T family
- The lint filter, condenser or vent is restricted — First. Clean the filter, check the condenser unit if the model has one, and confirm the exhaust is actually blowing before anything is suspected inside the machine.
- Half the electrical supply is missing — Worth checking early, because it is a breaker at the panel rather than a part in the machine.
- A thermal fuse or a safety thermostat has opened — If the drum turns and there is no heat at all after a period of restricted airflow, this is the likeliest single component.
- The heating element or the gas valve has failed — Fourth, and the point at which the job stops being an owner one on any of these models.
- On a gas model, the igniter or flame sensor has failed — Relevant only to gas models, and never an owner diagnosis: confirm the gas supply is on and hand the rest over.
Check in this order, and why
- Clean the filter and confirm the exhaust is blowing — Hold a hand at the outlet while the machine runs. Weak flow is the fault, or at least the cause of the fault, and no part fitted inside will survive it.
- Check both halves of the breaker at the panel — On an electric dryer, switch the breaker fully off and back on.
- On a gas model, confirm the shut-off valve is open — That is the whole of the owner-side gas check. If the valve is open and the burner does not light, stop there and call — do not open the burner area.
- Try a high-heat timed cycle — It removes the sensing circuit from the picture. No heat on a timed high cycle confirms the fault is in the heat path rather than in the cycle logic.
- Stop at the panel — Thermal fuses, thermostats, elements, gas valves and igniters all sit behind panels, need the machine isolated, and on a gas model need the gas closed.
Models in the T family — Each code here is pinned to a single build, so match the tag inside your door frame character for character.
Reference| Model number | Family key |
|---|---|
| T21 | bosch:dryer:t |
| T27 | bosch:dryer:t |
Before you open anything
Safety
Switch off the breaker before any panel comes off — a capacitor can hold a charge after the power is off. On a gas model close the shut-off valve first, and if you smell gas at any point do not switch anything on or off: leave the building and call the gas utility from outside.
When to call a technician
Call once the filter is clean, the exhaust is blowing properly and the breaker has been reset, and the drum still turns cold. On a gas model, call as soon as the shut-off valve is confirmed open and the burner still does not light — the burner is not an owner area on any of these models.
Other symptoms covered for this family
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
