BoilerFaultCodesYour boiler has stopped working because the internal pump that moves water around your heating system has become stuck or failed.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: The display shows alternatively the CH flow temperature and 9A. The pump is blocked. See error E9.
What causes this fault?
This fault occurs when the boiler's internal pump is unable to spin, preventing hot water from leaving the unit. The most common reason is a build-up of black iron oxide sludge that physically jams the moving parts, or an electrical failure within the pump motor itself. Without a working pump, the boiler shuts down immediately to prevent the internal heat exchanger from overheating.
This fault is frequently seen at the start of autumn when heating systems are turned back on after being idle all summer, allowing settled debris to seize the pump.
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 9A — 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.