CH light on PCB 40 flashing High

Ideal CH light on PCB 40 flashing Fault Code

Also written as CHLIGHTONPCB40FLASHING — same fault.

The Ideal CH light on PCB 40 flashing fault code means: your boiler has detected a communication problem or a fault with the sensor that controls your central heating temperature.. It appears on 1 Ideal model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Check the CH sensor and panel control and/or the wires connecting them to the PCB.

What causes the Ideal CH light on PCB 40 flashing fault?

This fault occurs when the boiler's main computer loses touch with the sensor that monitors your heating water temperature. It usually happens because the sensor has failed internally or the electrical wires connecting it to the control board have become loose or damaged. Without this vital temperature data, the boiler shuts down as a safety precaution to prevent overheating.

This fault often appears when the heating is first turned on in autumn, as the sudden change in temperature can cause aging electrical sensors to fail.

Typical repair cost £90-180 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Ideal models that show the CH light on PCB 40 flashing fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Ideal CH light on PCB 40 flashing 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