High Lockout
ERROR CODE 5 on Ideal Icos HE

Your boiler has detected a problem with the internal sensor that monitors the temperature of the water for your radiators.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

CH THERMISTOR FAULT

What causes this fault?

This fault occurs when the internal sensor responsible for tracking the temperature of the water leaving the boiler becomes faulty or disconnected. The most common reason is that the sensor has suffered electrical failure over time or the wiring connecting it to the main control board has developed a loose connection, preventing the boiler from safely regulating heat.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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