Key Takeaways
- A clogged lint filter or heat exchanger is the most common cause
- Heat pump dryers lose heating efficiency gradually — condenser dryers fail suddenly
- Error codes F36 and F66 point to NTC sensor or heater relay problems
- Always check airflow paths before assuming a component failure
The Bottom Line
If cleaning the lint filter and heat exchanger does not restore heat, the problem is likely a failed NTC sensor (From $100) or heater relay (From $150). Both are economical repairs on Miele dryers.
Is This Urgent?
Not dangerous, but do not keep running the dryer hoping it fixes itself. Running without proper heat wastes energy, extends cycle times dramatically, and on heat pump models can strain the compressor — the most expensive component to replace.
Most Common Causes
1. Clogged Lint Filter (Most Common)
A lint-clogged filter restricts airflow so severely that the dryer cannot transfer heat to the clothes. On heat pump models, restricted airflow causes the compressor to cycle off on thermal protection, resulting in cold air. Clean the filter before every cycle — this single step prevents the majority of “not heating” complaints.
2. Dirty Heat Exchanger (Heat Pump Models)
Fine lint that passes through the filter accumulates on the heat exchanger fins over weeks. Open the service door at the bottom-front of the machine, slide out the heat exchanger, and rinse under running water. This should be done monthly.
3. Failed NTC Temperature Sensor
The NTC sensor monitors air temperature inside the drum. If it reads incorrectly, the control board either does not activate the heater or shuts it off prematurely. Error code F36 typically indicates this problem. Replacement cost: From $100.
4. Heater Relay or Element Failure
On condenser and vented models with a resistive heating element, the element itself can burn out (open circuit) or the relay on the control board can fail. Symptoms: the drum turns and the fan runs, but there is zero heat. Element replacement: From $120. Relay repair: From $150.
5. Blocked Exhaust Duct (Vented Models)
A blocked or crushed exhaust duct causes the thermal overload to trip, cutting power to the heating element. Check the full duct run from the dryer to the exterior vent for lint accumulation, kinks, or obstructions.
What You Can Check Yourself
- Clean the lint filter thoroughly
- Clean the heat exchanger (heat pump models)
- Check the exhaust duct for blockages (vented models)
- Empty the condensation tank
- Run a short cycle on high heat and check if the drum air feels warm after 10 minutes
When to Call a Professional
- Lint filter and heat exchanger are clean but there is still no heat
- Error codes F36, F66, or F40 appear on the display
- The dryer trips the household circuit breaker
- You smell burning or see scorch marks on the plug