Error E03

Safety precautions:

- If you smell gas, do not operate electrical switches or the boiler. Evacuate the property and call the gas emergency number immediately.

- If you are in any doubt about safety, isolate the gas supply at the meter and call a Gas Safe engineer.

- Do not attempt to remove or dismantle the gas valve, undo gas unions, or carry out any gas-tightness, combustion or pressure checks unless you are a Gas Safe registered engineer.

- Turn off mains power to the boiler before opening the casing if any visual internal checks are to be carried out, and only if you are competent to do so. Preferably leave internal checks to an engineer.

Initial homeowner checks you can safely do:

1. Note the exact error code and any additional display messages. Take a photo of the display and the boiler rating/serial plate for the engineer.

2. Try a simple reset: press the boiler reset button (or switch the boiler off at the isolator for 1 minute and back on) and see if the code returns. If the fault is intermittent the boiler may restart once but will lockout again if the underlying issue remains.

3. Check the mains supply to the boiler (is the display lit?). If the boiler has no power, check the fused spur, RCD/fuse box and a local switched isolator.

4. Check the property gas supply: confirm other gas appliances (hob, gas fire) work. If no gas to the house, contact your gas supplier. Do not attempt to test gas pressure yourself.

5. If you see corrosion, water ingress or disconnected external wiring where it is obviously safe and external (for example at a removable control panel connector), photograph it and report it to the engineer. Do not unplug internal push-on connectors or wiring if you are not competent.

If the E03 persists (what the engineer will do - for information only):

- A qualified engineer will isolate gas and power, remove the boiler case and check the gas valve electrical connector (push-on connector) is fitted and free of corrosion, and check wiring continuity to the control PCB and fascia.

- The engineer will measure inlet gas pressure at the gas valve (typical reference ~20 mbar) and check the valve drive signal from the control board during an ignition attempt. They will also confirm the igniter and flame detection circuit are functioning so the valve is being commanded correctly.

- If the valve is electrically connected but does not respond or does not pass the correct gas flow, the valve assembly may need replacing. If the control PCB is not commanding the valve correctly the control box may be at fault and require repair or replacement.

- After any replacement, the engineer will carry out boiler tightness checks, combustion/CO tests and commissioning checks as required by gas safety regulations.

When to call a professional and other notes:

- Call a Gas Safe registered engineer whenever E03 is displayed and it does not clear after a safe reset and basic checks. This fault involves gas components and cannot be safely repaired by an unqualified person.

- If your boiler is under warranty, contact Keston authorised service or the warranty hotline first — do not use an unapproved engineer if warranty terms require manufacturer service.

- Record what you tried, the exact code, and any accompanying codes or symptoms to give the engineer when they attend. This helps speed diagnosis.

Remember: do not attempt to replace or adjust the gas valve or its gas unions yourself. That work must be completed by a Gas Safe registered engineer who will perform the necessary safety and combustion checks.