F4
Ideal Ignition Failure

Ideal boiler shows F4 and fails to ignite; no flame is established.

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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

Faulty ignition electrode or lead, Incorrect electrode gap or position, Gas valve not opening, Low or no gas supply to the boiler

How to Fix / Troubleshooting

Safety first: Ignition and gas valve issues must be handled by a Gas Safe registered engineer. Do not remove the boiler casing or attempt to access the burner.

User checks:

  • Confirm gas supply: Check other gas appliances. If they do not work, contact your gas supplier.
  • Check boiler controls: Ensure the room thermostat and programmer are calling for heat and that the boiler is not in standby or holiday mode.
  • Reset the boiler: Turn the boiler off and on, then press the reset button once. Do not repeatedly reset if F4 returns immediately.

Engineer tasks (for information):

  • Inspect and clean the ignition electrode and check spark strength.
  • Verify the correct electrode gap and positioning relative to the burner.
  • Test gas valve operation and inlet pressure.
  • Check wiring between the ignition transformer and PCB.

If F4 persists, stop resetting and arrange a visit from a Gas Safe registered engineer.

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Repair Difficulty

Professional Required 5/5

Required Part

Ignition Electrode
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