BoilerFaultCodesYour boiler is not receiving enough electricity from the power grid to operate properly, causing it to shut down for safety.
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 under 170V – electric mains error
What causes this fault?
This fault occurs when the electrical supply entering your home drops below the minimum level required for the boiler's internal components to function. It is usually caused by an external problem with the local power grid or a fault within your home's consumer unit that is starving the boiler of steady power. In some cases, a deteriorating main circuit board inside the boiler can also misread a healthy voltage as being too low.
This fault can be more common during period of extreme weather or high national energy demand, when the local electrical grid may experience temporary 'brownouts' or voltage fluctuations.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like F34 — 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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