Boiler shuts down shortly after starting; E02 displayed; overheat or high temperature lockout

Safety first: Turn off electrical power to the boiler before removing any covers. Allow the boiler to cool fully before touching any pipework.

User checks:

• System pressure: Check the pressure gauge on the Dimplex boiler. It should typically be around 1.0–1.5 bar when cold (check your manual). If below 1.0 bar, top up via the filling loop according to the manufacturer’s instructions, then reset the boiler.
• Bleed radiators: Air in the system can cause local overheating. With the boiler off and cool, bleed radiators starting from the lowest floor. Recheck and adjust pressure afterwards.
• Ensure valves are open: Confirm that the Dimplex flow and return isolation valves under the boiler and any zone valves are fully open.

Professional checks:

• Test and replace the Dimplex primary NTC sensor if readings are out of range.
• Inspect and clean or replace the Dimplex plate heat exchanger if blocked with sludge or scale.
• Check the Dimplex circulation pump for operation, free rotation, and correct speed setting; replace if seized or weak.