E9 is displayed and the unit shuts down shortly after starting.

Safety first: Unplug the air fryer immediately. Do not repeatedly reset and run the unit if it trips E9, as this may indicate an electrical short.

• Visual inspection: Remove the rear cover and inspect the wiring harnesses, heater, and fan for obvious burn marks, melted insulation, or arcing.
• Check for shorts to chassis: With a multimeter in continuity mode, check between each heater lead and the metal chassis. There should be no continuity. Repeat for the fan motor leads.
• Isolate components: Disconnect the heater and fan from the control board. Plug in the unit (do not start a cook cycle) to see if E9 appears. If E9 clears with components disconnected, reconnect one at a time to identify the shorted part.
• Replace faulty component: Replace any component that shows a short to ground or extremely low resistance across its terminals (heater or fan motor).
• Control board check: If no external component is shorted, the main control PCB power supply or triac/relay may be internally shorted and the board should be replaced.

Because this involves mains voltage and potential fire risk, consider professional service if you are not experienced with electrical diagnostics.