BoilerFaultCodes.com
A(5) High Lockout

Your boiler is unable to create the spark needed to light the flame, which means your heating and hot water will not work.

Call an engineer soon

Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Igniter generator not working

What causes this fault?

This fault occurs when the boiler's internal computer sends a signal to start the fire, but no spark is physically generated to ignite the gas. The most common reason is that the electronic ignition component has failed or the spark electrode has become worn or cracked over time. Without this initial spark, the boiler cannot light safely and will shut down to prevent unburnt gas from building up.

Typical repair cost £120-£240 (including labour)

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 A(5) — no call-out fees, no surprises.

Top rated
OpenFix
Boiler & heating care plans
Get a quote →
Hometree
from £12.95/month
Get a quote →
HomeServe
from £8.00/month
Get a quote →

Affiliate links — we may earn a commission at no extra cost to you.

Potterton Flamingo RS40 RS50 is discontinued — time for a new one?

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.

UK's #1 online installer
Boxt
Fixed-price online quotes. Next-day installation.
Get a free quote →
Heatable
Instant online boiler quotes from £1,499.
Get a free quote →
iHeat
Fast installation. Price match guarantee.
Get a free quote →

Affiliate links — we may earn a commission at no extra cost to you.

Related fault codes