Display shows H0 or HO and the unit does not heat, though the fan may run.

Safety first: Unplug the air fryer and allow it to cool. Work carefully around mains-voltage components.

Verification:

• Start a cooking cycle and listen for a click from inside the unit. Lack of a click may indicate the heater relay is not energizing.
• Check that the fan runs; if the fan runs but there is no heat and H0 is displayed, the heater circuit is likely not being switched on.

Internal inspection (advanced):

• Remove the housing to access the main control PCB.
• Locate the heater relay (a small rectangular component, often labeled with coil voltage and contact ratings).
• Inspect for burn marks, cracked casing, or discolored PCB around the relay.
• Resolder any cracked or dull solder joints on the relay pins.
• If you have a multimeter and experience, test for voltage at the heater terminals when a cycle is started. No voltage with a command to heat indicates a relay or drive circuit fault.
• Replace the heater relay if you are capable of desoldering/soldering, or replace the entire main control board if component-level repair is not practical.

Because this involves live mains circuits, many users will be safer replacing the full control board or using professional service.