F3
Ultima Cosa Heater Drive Circuit Error

F3 appears and the unit will not heat; fan may still run.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Failed heater triac or relay on main PCB, Open circuit between board and heater, Incorrect feedback from temperature sensor during heater test, Burned PCB trace on heater output

How to Fix / Troubleshooting

Safety first: Unplug the air fryer and allow it to cool. High voltage is present on the heater circuit.

  • Check heater and wiring: Verify heater continuity and inspect wiring as in heater-related entries. Repair any open connections.
  • Inspect PCB heater output: Look at the main control PCB around the heater relay/triac. Check for burnt traces or cracked solder joints. Resolder cracked joints if you are experienced.
  • Replace control board: If the heater and wiring are good but F3 persists, the heater drive component on the PCB is likely faulty. Replace the main control PCB with a compatible Ultima Cosa part.

Because this involves mains switching components, board-level repair is best left to professionals; most users should replace the entire board.

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Repair Difficulty

Hard 4/5

Required Part

Main Control PCB
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