BoilerFaultCodesYour boiler has been left in a manual testing mode after a recent service or inspection, which is preventing it from running normally.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Check service mode switch is in minimum position
What causes this fault?
This fault occurs because the internal manual control wheel, often used by engineers during a service to test the system, has been left in a specific test position rather than the 'run' position. Because the boiler thinks it is still being manually tested for performance, it will not respond to your normal thermostat or hot water requests. It is essentially stuck in a maintenance mode that disables its automatic functions.
DIY fix possible
Locate the service mode switch on the boiler control panelCheck if the switch is set to the maximum or chimney sweep iconReturn the switch to the vertical 'off' or 'minimum' position to restore normal operation
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 2 pulses — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.