Boiler will not start; lockout light on; E01 displayed on Dimplex control panel

Safety first: If you smell gas, do not attempt any repair. Turn off the gas at the isolation valve, switch off power to the boiler, ventilate the area, and contact a Gas Safe–registered engineer immediately.

Basic checks you can do:

• Reset the boiler: Turn off the boiler at the fused spur for 30 seconds, then turn it back on and press the reset button on the Dimplex control panel if available. Observe if E01 reappears.
• Check gas supply: Ensure other gas appliances (if present) work. Confirm the gas isolation valve near the boiler is fully open.
• Inspect the flue terminal: From outside, make sure the Dimplex concentric flue terminal is not blocked by debris, snow, or vegetation, as poor combustion can prevent flame detection.
• Check for visible damage: With power isolated, remove the front cover only if your model allows user access. Look for loose ignition lead connections to the spark electrode and obvious burn marks. Do not dismantle the sealed combustion chamber.

When to call a professional:

• If E01 persists after a reset.
• If the burner does not ignite or ignites then shuts down within a few seconds.
• A qualified technician should test and, if necessary, replace the Dimplex flame sensor (ionisation electrode), ignition transformer, or gas valve assembly, and verify gas pressure and combustion using a flue gas analyser.