BoilerFaultCodesIdeal 436 Fault Code
The Ideal 436 fault code means: your boiler has stopped working because a sensor that monitors the water temperature has disconnected or broken.. It appears on 2 Ideal models in our database.
Technical description: NTC 1 open
What causes the Ideal 436 fault?
This fault occurs when the boiler's control board loses communication with the sensor that monitors the temperature of the water leaving the unit. The most common reason is that the internal sensor has developed an electrical failure or the wiring connecting it to the main board has become loose or damaged. Without this data, the boiler shuts down as a safety precaution to prevents the system from overheating.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Ideal models that show the 436 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal 436 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