BoilerFaultCodesYour boiler is not receiving enough electricity from the mains supply to operate its electronic components 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 under 170v – electric supply error
What causes this fault?
This fault occurs when the electrical current entering your boiler drops to an unsafely low level, preventing the internal computer from functioning. The most common reason is a wider problem with the local power grid or a fault in your home's electrical wiring, though a failing internal circuit board can sometimes misread a healthy supply.
This fault can occasionally occur during extreme winter peaks when the national grid experiences exceptionally high demand, leading to temporary 'brownouts' or voltage drops.
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 F34 — 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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