Dryer does not heat; cycle runs but clothes stay cold and E04 appears on the display.

Safety first: Disconnect power before accessing the rear panel or heater assembly. Heating elements can have sharp edges.

• Confirm no heat: Run a short cycle and check if any warm air is produced at the exhaust or inside the drum. If completely cold, proceed with heater checks.
• Access heater assembly: Remove the rear panel (or side panel on some models) to expose the heater housing. Visually inspect the heating element for breaks or burn marks.
• Test heating element: Disconnect the element terminals and measure resistance with a multimeter. An open circuit indicates a failed heating element that must be replaced with a compatible De Dietrich part.
• Check wiring and connectors: Inspect the heater wiring harness and connectors for signs of overheating, discoloration, or loose fit. Repair or replace damaged wiring and ensure tight connections.
• Control board relay: If the element and wiring are good, the heater relay on the main control board may be defective. Look for burnt spots on the PCB. Board replacement is usually required and should be done by a qualified technician.
• NTC sensor check: Some models monitor heater temperature via an NTC sensor on the heater housing. Test its resistance against service manual values. Replace the heater NTC sensor if out of range.