E4 appears on the display and the unit will not heat; fan may still run.

Safety first: Disconnect power and allow the air fryer to cool. The heater circuit carries mains voltage and can be dangerous.

Diagnostic steps:

• Visual inspection: Remove the top cover to expose the heating element. Look for obvious breaks in the coil, burn marks, or discolored connectors.
• Check heater continuity: With a multimeter, measure resistance across the two heater terminals. An infinite reading indicates an open heating element.
• Inspect connectors and wires: Tug gently on the spade connectors at the heater. Replace any that are loose, burned, or brittle. Use high-temperature rated wire and terminals.
• Check the heater relay: On the main control PCB, locate the heater relay (often labeled with a heater symbol). Look for burn marks or cracked solder joints. Resolder any cracked joints if you are experienced with electronics.
• Replace the heating element: If the coil is open, install a new T-fal heating element assembly specific to your model. Transfer any attached thermal sensors or brackets to the new element.

If the heater and wiring test good but E4 persists, the main control PCB may need replacement.