Air fryer displays E4 and will not start a cooking cycle.

Safety first: Unplug the unit. Do not attempt to bypass any safety devices. Thermal fuses and cutoffs are critical safety components.

Steps to address E4:

• 1. Allow full cool-down: Let the air fryer sit unplugged for at least 45–60 minutes to ensure all internal components are at room temperature.
• 2. Access thermal cutoff: Remove the back or bottom cover. Locate the thermal fuse / thermal cutoff in series with the heating element wiring, often wrapped in heat-resistant sleeving near the element.
• 3. Visual and continuity check: Look for discoloration or burn marks. If you have a multimeter, test the thermal fuse for continuity. An open reading indicates it has blown.
• 4. Inspect for root cause: Before replacing, inspect the heating element and surrounding area for signs of shorting, grease fires, or melted insulation. Correct any obvious damage or wiring issues.
• 5. Replace the thermal fuse: Obtain a matching Granitestone thermal fuse / cutoff with the same temperature and current rating. Cut out the old fuse and crimp or solder in the new one using high-temperature connectors. Do not bypass or use a lower-rated part.
• 6. Test operation: Reassemble the housing, plug in, and run a short test cycle while monitoring for unusual smells or smoke. If E4 persists, the control PCB may be locked in an error state or damaged and should be replaced by a professional.