Air fryer displays E4 and will not start heating.

Safety first: Unplug the air fryer. Internal components may still be hot; wait until fully cooled.

• Inspect airflow and cleanliness: Before replacing parts, remove the basket and drawer and clean heavy grease from the cavity, especially around the heater and fan guard. Ensure all external vents are clear.
• Access thermal fuse: Remove the top or rear cover (depending on model) to access the heater assembly. The thermal fuse is usually a small cylindrical or capsule-shaped component in series with the heater wiring.
• Test continuity: With a multimeter, check continuity across the thermal fuse. If it reads open (no continuity), it has blown and must be replaced with an identical temperature and current rating component.
• Check high-limit thermostat: If present, test the bimetal thermostat for continuity at room temperature. It should be closed. If open, replace the thermostat.
• Reassemble and test: After replacing the thermal fuse and/or thermostat, reassemble the unit, plug it in, and run a short preheat. Monitor for any burning smell or abnormal heat. If E4 persists, the main PCB may be misreading the protection circuit and should be evaluated by a technician.