BoilerFaultCodesYour boiler is struggling to move water around the system effectively, causing it to overheat and shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Pump Fault or Primary Circulation Problem / burner lighting boiler temperature has not changed by 1° within 15 seconds or exceeds selected temperature by 30° twice within 10 minutes
What causes this fault?
This fault occurs when water is not moving through the boiler fast enough to take the heat away from the internal heat exchanger. The most common reason is a failed internal pump or a blockage in the system pipes, which causes the temperature to spike too quickly and triggers a safety shutdown. It can also be caused by a faulty sensor giving the boiler incorrect information about how hot the water actually is.
This fault is more frequent during the first cold snap of autumn when heating systems are turned back on after being idle all summer, which can cause internal pump components to seize.
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 E125 — 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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