Display shows E4 and the unit will not start or stops mid‑cycle.

Safety first: Unplug the air fryer and allow it to cool completely. Internal components near the heater can remain hot for a long time.

• Step 1 – Visual inspection: Remove the basket and drawer. Look up toward the heater for heavy carbonized grease or food debris. Clean thoroughly with a non‑abrasive sponge and degreaser, avoiding soaking electrical parts.
• Step 2 – Access heater assembly: Remove the top or rear cover (model dependent) by taking out the screws. Locate the thermal fuse and/or bimetal thermostat attached to the heater shroud.
• Step 3 – Check continuity (for experienced DIYers): With the unit unplugged, disconnect one lead of the thermal fuse and test with a multimeter. An open reading means the fuse has blown and must be replaced; it is not resettable.
• Step 4 – Replace blown thermal fuse: Match the temperature and current rating printed on the original Ambiano thermal fuse. Crimp or spot‑weld the new fuse; do not solder directly to the fuse body as heat can damage it.
• Step 5 – Verify fan operation: Before reassembly, spin the fan by hand to ensure it moves freely. A seized or slow fan can cause repeated overheating.
• Step 6 – Reassemble and test: Refit all covers and screws, plug in, and run a short test at a moderate temperature. If E4 returns quickly, the main control PCB or thermostat calibration may be faulty and professional service is recommended.