Low Information
SH on Ideal Logic Combi C24 C30 C35

Your boiler is not in a fault state; it is simply running in a manual test mode designed for service engineers to check its performance.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

Fault history mode diagnostic code

What causes this fault?

This code appears because the boiler has been manually put into 'Service Mode' by a person pressing specific buttons on the control panel. It is a deliberate setting used to force the burner to its maximum power so an engineer can test the gas pressure and emissions. It is not caused by a mechanical failure or a broken internal part.

DIY fix possible

Press and hold the 'Preheat' and 'i' buttons together for 5 seconds.Restart the boiler using the power dial or reset button to exit the test mode.The display should return to the standard temperature or 'D' / 'C' status.

Find a Gas Safe engineer
Search the official register →

Related fault codes

SLView →

Related guides you might find useful

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

New boiler cost 2026

Realistic UK prices for a swap.

Read →