BoilerFaultCodesYour boiler is not receiving enough electrical power from your home's mains supply to operate safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Supply voltage is below low limit
What causes this fault?
This fault occurs when the electrical supply entering your boiler drops below the minimum level required for its internal components to function correctly. It is often caused by instability in the local power grid, a faulty electrical connection within your home, or a failing internal control board that can no longer process the incoming voltage.
This issue can be more frequent during periods of extreme cold or heatwaves when the national grid is under heavy load, potentially causing 'brownouts' or voltage fluctuations in residential areas.
DIY fix possible
Check if there is a power cut or brownout in your local areaEnsure your fuse box / consumer unit has not trippedTurn the boiler off at the fused spur switch, wait 30 seconds, and turn it back on to reset the electronics
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 JJ-64 — 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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