E09 appears; unit may heat briefly then shut off, or may not heat at all while fan runs.

Safety first: Unplug the appliance. Control board work involves mains voltage; proceed only if you are experienced with electronics.

Steps:

• 1. Confirm heater function: If possible, test the heating element separately for continuity to ensure it is not open. If the heater is good, focus on the control board.
• 2. Access control PCB: Remove the housing to expose the main control board. Note all connectors and take photos before disconnecting.
• 3. Visual inspection: Look for a small relay or triac labeled for the heater circuit. Check for burn marks, cracked casing, or darkened PCB around it.
• 4. Solder joints: Inspect the underside of the board for cracked or dull solder joints on high‑current paths. Reflow with solder if you are skilled and have proper tools.
• 5. Board replacement: If the relay or triac is visibly damaged or testing confirms failure, the recommended repair is to replace the entire control board with a Bosch‑approved spare.

Warning: Improper repair of mains circuitry can cause electric shock or fire. If unsure, seek professional service.