Bella air fryer beeps and displays E4 shortly after starting a cooking cycle.

Safety first: Always unplug the unit before opening any panels. Do not continue to run the air fryer if it repeatedly shows E4; low voltage can overheat components.

External checks:

• Plug the air fryer directly into a wall outlet with no extension cord or power strip.
• Avoid sharing the circuit with other high‑draw appliances (microwave, toaster oven, space heater).
• If lights dim when the air fryer starts, have an electrician check the circuit for loose connections or overload.

Internal checks:

• Unplug the unit and remove the cover to access the internal wiring harness and control board.
• Inspect all push‑on connectors from the power cord to the control PCB and from the PCB to the heater and fan. Reseat any loose connectors.
• Look for heat damage or discoloration on the board near the AC input and transformer or switching power supply section.

If E4 persists on a known‑good outlet with solid wiring, the main control PCB is likely misreading line voltage and should be replaced. Component‑level repair is not recommended unless you are experienced with mains‑voltage electronics.