E4 appears on the display and the air fryer does not heat or shuts off quickly.

Safety first: Unplug the appliance and confirm it is completely cool.

Check the heating element:

• Remove the top or rear cover to access the heating element assembly.
• Visually inspect the element for breaks, burn marks, or warping. Check the ceramic insulators and terminal lugs.
• Use a multimeter to measure resistance across the element terminals. A typical element will show a finite resistance (often 10–60 Ω). If it reads OL (open), the element is failed and must be replaced.
• Inspect and tighten the spade connectors at the element and at the control board heater relay. Replace any overheated or discolored connectors.

Control board relay:

• If the element tests good, check for 120 V (or local mains voltage) at the element when the unit is calling for heat (this test should only be done by someone experienced with live-voltage measurements).
• If no voltage is present and wiring is intact, the heater relay or triac on the control board is likely defective and the main control board should be replaced.

Warning: Do not bypass safety thermostats or fuses to force the heater on; this is a fire hazard.