BoilerFaultCodesYour boiler has switched itself off because the water returning to the unit is too hot, meaning the heat isn't being distributed around your home properly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Maximum temperature - Return temperature T2 too high
What causes this fault?
This fault occurs when the water returning to the boiler is almost as hot as the water leaving it, indicating that heat is not being transferred into your radiators or cylinder. The most common reason is a failure of the external pump or a blockage in the pipework that prevents the water from circulating through your heating system. It can also be caused by all your radiator valves being closed at the same time, leaving the hot water with nowhere to go.
This fault is more common in autumn when heating systems are turned back on after a long summer break, as external pumps can seize up due to inactivity.
DIY fix possible
Ensure all radiator valves (TRVs) are fully open to allow water to circulateCheck that your external pump (if applicable) is running and hasn't seizedInspect the system's bypass valve to ensure it isn't closed or blocked
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 919 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Ideal Systemiser SE 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.
Affiliate links — we may earn a commission at no extra cost to you.