BoilerFaultCodesYour boiler is currently running a manual test mode that forces it to operate at its maximum power for maintenance purposes.
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: Service Function: Max. heating output
What causes this fault?
This code appears because a service engineer has manually activated the 'chimney sweep' mode using the boiler's internal settings. It is not actually a fault, but rather a deliberate setting that forces the burner to run at full power so that gas pressure and emissions can be accurately tested. If you see this code and an engineer is not present, the service switch may have been left in the wrong position or bumped accidentally.
DIY fix possible
Locate the service buttons on the control panel.Press and hold the 'Reset' or 'Service' button for a few seconds to exit the test mode.Switch the boiler off and back on at the fused spur switch to reset the software.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like 5.0 — no call-out fees, no surprises.
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Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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