The short answer
A Miele heat-pump dryer that runs cool or takes far too long is nearly always choked with lint at the heat exchanger behind the plinth door — not a failed heating element, because it does not have one. The door filters and the water container come first because they are quicker. All three are owner cleans; only a sealed-system or fan fault is a service call.
What you observe
- Cycles that get steadily longer month by month — Falling airflow. The exchanger is loading up with lint.
- Clothes come out damp at the end of a full programme — Either airflow or the condensate path.
- The drum air feels barely warm — Normal for a heat pump, so judge by drying time instead.
- A full water container, or a warning about it — The condensate has nowhere to go. Quick to fix.
- NEAR MISS — the drum does not turn at all — That is a belt or motor fault, not a heating one.
Causes, most likely first on this brand
- Heat exchanger blocked with lint — First by a very wide margin on this platform, because the exchanger sits downstream of the door filters and catches whatever they miss. Many owners never learn it is there, so it silts up over years.
- Door filters loaded or fitted badly — Second: they are the first line of defence, and a filter refitted a fraction proud lets lint straight past it into the exchanger.
- Condensate container full, or its drain path blocked — Third. The machine stops or leaves the load damp rather than heating badly, which is how you tell it apart from an airflow fault.
- Fan, compressor or sealed-system fault — Last, and the only one that is not owner work. Ranked here because on a heat-pump machine the sealed system is far more reliable than the lint path in front of it.
Check in this order, and why
- Empty the water container and note whether it was full — Fastest possible answer to a damp-load complaint.
- Pull and clean both door filters — Free, quick, and they feed everything downstream.
- Open the plinth door and look at the heat exchanger — The top cause, and most owners have never looked.
- Compare cycle time now with when the machine was new — Left until here, but a lengthening trend confirms airflow.
What an owner can safely check
- Empty the condensate container and refit it squarely — Check the drain hose route if yours is plumbed.
About 5 min
- Remove and rinse both door filters, then dry them — Refit flush. A proud filter lets lint past.
About 15 min
- Open the plinth door and clean the exchanger face — Vacuum gently, or rinse if yours is removable. Never poke the fins.
Tools: vacuum, soft brushAbout 30 min
- Wipe the seal and the recess the plinth door closes on — Lint there stops the door sealing and short-circuits airflow.
Tools: clothAbout 10 min
- STOP HERE if the next step means opening the cabinet — Fan and sealed-system work is technician work.
Before you open anything
Safety
Unplug the dryer or switch off its breaker before opening the plinth or any panel; a capacitor can hold a charge after the power is off. Let the machine cool before reaching inside, because the exchanger and the ducting stay warm after a cycle. Never straighten heat-exchanger fins with a screwdriver or a knife — they are thin aluminium over refrigerant tubing, and piercing one ends the machine. Dry the floor before restoring power.
When to call a technician
Call when both filters and the exchanger are clean, the container empties properly and the machine still runs long or leaves loads damp — the fan or the sealed system is then the answer and neither is owner work. Call sooner if the drum does not turn, which is a different fault entirely. Call immediately, with the machine unplugged, if you smell hot insulation or scorched lint during a cycle.
Nearest pages of this class
What this page does not cover
This page is written for the brand and the appliance class, not for one family or model line. Where a family- or model-specific page exists for your unit, that page is the more specific answer and you should start there. Deliberately absent: exchanger and fan part identifiers, refrigerant charge figures, drying temperatures, programme durations and fault-code meanings, all of which differ between the heat-pump, condenser and vented families.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
