BoilerFaultCodesYour boiler has detected an unstable incoming electrical supply that is either too high or too low for it to run safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: High Voltage or Low Voltage Error
What causes this fault?
This fault occurs when the electrical current entering the boiler fluctuates outside of its safe operating window, which can be caused by local power grid issues or a faulty transformer. It can also be triggered by loose internal wiring or a failing printed circuit board that can no longer accurately monitor the incoming power. If your home has recently experienced a power surge or a brownout, the boiler’s safety system will automatically shut down to prevent sensitive components from burning out.
This fault is slightly more common during stormy weather or periods of high grid demand, as lightning strikes or local power surges are more likely to destabilise the electrical supply.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 High Voltage or Low Voltage Error — no call-out fees, no surprises.
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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.
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