Error A1 281

Safety first

- If you are unsure at any point, stop and call a Gas Safe engineer. Do not work on gas appliances beyond simple user tasks. Isolate electrical power to the boiler at the isolator or fused spur before touching internal components or any plumbing inside the boiler casing. Do not attempt to replace the pump or access gas components unless you are a qualified engineer.

Initial quick checks a homeowner can do

1) Note the fault code (A1 281), any flashing lights and when it started. This information is useful to an engineer.

2) Try a reset following your boiler manual. If the code clears and the boiler runs normally, monitor for recurrence. A reset is only a temporary measure if the underlying fault remains.

3) Check the boiler pressure gauge when the system is cold. Normal is about 1.0–1.5 bar. If pressure is low (below ~1.0 bar), top up the system using the filling loop: open the filling loop valves slowly until the pressure reaches about 1.2 bar, then close the valves securely. Re-check for leaks after topping up and then reset the boiler.

4) Look for visible leaks around the boiler, pipes, radiators and valves. A continuous drop in pressure indicates a leak that must be fixed by an engineer.

5) Bleed radiators to remove trapped air. Start with the highest radiators in the house and work downwards. Use a radiator key, collect water with a cloth, and close the bleed valve once water flows steadily. Re-check system pressure and top up if required, then reset the boiler.

Diagnostics and specific checks

6) Listen to the pump: with the boiler powered and calling for CH, check if the pump is humming or vibrating. If completely silent when it should be running this suggests an electrical fault or a seized pump. If it hums but there is no circulating heat and radiators are cold, there may be an airlock, blockage or seized impeller.

7) If you have an external/system magnetic filter that is user-serviceable, isolate and drain the small section of system per the manufacturer’s instructions and clean the filter magnet of debris. Many magnetic filters are intended to be cleaned by the homeowner but only do this with the boiler and pump isolated and if you are confident with the isolation/drain steps.

8) Try to purge air from the pump area: after isolating the boiler electrical supply (power off), some systems allow a small bleed point near the pump or you can re-bleed nearby radiators to move air away from the pump. Do not open the boiler casing or attempt to manipulate the pump shaft unless the manual explicitly shows a safe user procedure.

9) Do not attempt pump shaft turning or internal pump maintenance unless you are trained. Some pumps have an allen key access to free a seized shaft, but this requires isolation of electrical supply and exposes you to internal components; performing this while inexperienced risks injury, further damage and may void warranties.

When to call a professional and what to tell them

10) Call a Gas Safe registered engineer if the A1 281 code persists after you have: reset the boiler, checked and topped up pressure, bled radiators, and checked for visible leaks and the system filter. Also call a pro if you find evidence of sludge, if the pump is hot or noisy, or if you are uncomfortable performing any of the checks above.

11) When you contact an engineer, give them: the exact error code (A1 281), boiler model, recent pressure readings, what you have already tried (reset, topped up, bled radiators), any noises from the pump, any leaks found, whether you have a magnetic filter, and how long the problem has been present. This helps speed diagnosis.

Likely engineer actions (for information only)

- A qualified engineer will perform electrical checks on pump supply and control wiring, test the pump for seizure and bearing wear, inspect and clean or replace the system/magnetic filter, and check for sludge or blockages. They will also check PCB signals and any controls (room stats, weather compensation) that could affect pump operation. If the pump is mechanically failed it will usually be replaced; if the system is contaminated a powerflush or chemical clean may be recommended.

Final note

- The initial homeowner checks above can resolve airlocks and low-pressure causes of A1 281, but do not attempt internal boiler repairs, pump replacement or gas-related work yourself. Persistent faults, electrical issues, seized pumps or internal cleaning/replacement must be carried out by a Gas Safe registered engineer to ensure safety and compliance.