BoilerFaultCodesIdeal 4C Fault Code
The Ideal 4C fault code means: your boiler has shut down because it has detected it is getting too hot or an internal safety fuse has blown.. It appears on 1 Ideal model in our database.
Technical description: Fuse F2 blown or temperature of burner thermostat too high or supply temperature too high.
What causes the Ideal 4C fault?
This fault occurs when the boiler's internal safety sensors detect that the unit is overheating or when an electrical surge has blown a protective fuse on the circuit board. It is often caused by a lack of water flow, a failing pump, or a build-up of debris blocking the heat exchanger, which prevents heat from being carried away from the burner. In some cases, the burner thermostat itself may have failed, incorrectly signaling a high-temperature situation.
This issue often surfaces at the start of autumn when the heating is turned back on after a long summer break, as pump components can seize during periods of inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Ideal models that show the 4C fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 4C fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026