BoilerFaultCodesYour boiler is struggling to control how much water flows through the system, which can prevent it from heating up correctly.
This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.
Technical description: The flow limiter is not properly adjusted.
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water is moving through the system at an incorrect speed, usually triggered by an improperly set flow regulator. The most common reason is that the mechanical limiter has shifted out of its calibrated position or has become blocked by internal debris, preventing the boiler from managing heat transfer safely. It can also be caused by a sensor failing to accurately report the water speed to the main control board.
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 43 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Ideal Maximiser 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.