BoilerFaultCodesYour boiler is not receiving enough electrical power from the main supply to operate safely and has shut down as a precaution.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Low mains supply voltage
What causes this fault?
This fault occurs when the electrical current entering the boiler drops below the level required for the internal components to function correctly. The most common reason is a fluctuation in the local power grid or a failing component on the control board that can no longer process the incoming voltage. In some cases, loose wiring or a faulty electrical socket can also prevent the unit from getting a steady stream of power.
This fault can be more common during peak winter months or during heatwaves when a high regional demand for electricity causes temporary 'brownouts' or dips in the local grid voltage.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like 34 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
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.
Affiliate links — we may earn a commission at no extra cost to you.