High Lockout
F17 on Ideal Logic Max System

Your boiler has detected that the internal pump, which moves water around your pipes and radiators, is not working correctly.

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

Pump Fault: Check pump wiring, if OK replace pump

What causes this fault?

This fault occurs when the boiler's control board detects that the internal pump is not spinning or drawing the correct amount of electricity. The most common reason is that the pump has seized due to a buildup of debris or sludge in the system water, or the motor has simply failed after years of heavy use.

This fault is more common in autumn when the heating is turned on for the first time after summer, as the pump can seize if it has been sitting idle for several months.

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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