E4 appears on the display and the air fryer will not heat or stops mid-cycle.

Safety first: Unplug the unit and allow it to cool completely. Internal heater wiring carries mains voltage; if you are not comfortable working with electrical components, contact a professional.

• Visual inspection: Remove the outer cover. Locate the heating element assembly at the top of the cooking cavity. Check for obvious breaks in the element coil, burnt spots, or disconnected wires.
• Check thermal fuse: Find the small cylindrical or flat thermal fuse mounted near the heater leads. Using a multimeter, test for continuity. If it is open (no continuity), replace it with an identical temperature and current-rated Crux-compatible thermal fuse.
• Inspect heater connections: Verify that spade terminals on the heater and thermal fuse are tight and not discolored or melted. Replace any overheated connectors and trim back burnt wire, using high-temperature wire and crimp terminals.
• Test heating element: With the unit unplugged and heater disconnected, measure resistance across the element. An infinite reading indicates an open element that must be replaced.
• If heater and fuse are good: The heater relay or triac on the main control PCB may have failed. Replacement of the main control PCB is required.