BoilerFaultCodesDimplex 1 Fault Code
The Dimplex 1 fault code means: your boiler has shut down because the water inside the unit has become too hot, likely due to a circulation problem or a blockage.. It appears on 3 Dimplex models in our database.
Technical description: Overheated appliance. CH Watertemperature greaterthan 105°C
DIY fix possible
Check that all radiator valves are fully openEnsure the boiler pressure is between 1.0 and 1.5 barSwitch the boiler off and back on to attempt a reset once the system has cooled down
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Dimplex models that show the 1 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Dimplex 1 fault code information on this page is sourced and cross-checked against the official Dimplex service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026