Error A1

Safety precautions:

- Before touching the boiler or any pipework, switch off the boiler and isolate the electrical supply at the fused spur. If you need to work on pipework that could involve gas or internal boiler components, do not attempt this yourself — call a Gas Safe engineer.

- Allow the boiler to cool and be careful of hot surfaces. Wear eye protection and gloves if you are bleeding radiators or working near hot pipes.

- Never tamper with gas components or attempt internal repairs unless you are a qualified engineer.

Initial checks a homeowner can do:

1. Check the pressure gauge on the front of the boiler when the system is cold. Normal is roughly 1.0–1.5 bar. If it is below 1.0 bar this can trigger A1.

2. Look for visible water leaks around the boiler, valves, pipework, radiators and under the appliance. A persistent drop in pressure usually means there is a leak somewhere.

3. Check the filling loop (if you have one) is fully closed and that the flexible hose and valves are intact. Ensure it is not left open after topping up.

4. Listen for the pump when the boiler runs. Signs of a pump problem include no sound when the pump should be running, a grinding noise, excessive vibration, or the pump casing feeling much hotter than normal.

5. Check radiators for cold tops/hot bottoms which indicate trapped air.

Simple corrective actions you can try:

1. Top up system pressure: If the pressure is low, follow your boiler manual to top up using the filling loop until the gauge reaches around 1.0–1.5 bar, then close the filling loop valves and re-check. If the filling loop is unfamiliar, consult the handbook — do not leave it open.

2. Bleed radiators: Starting at the top floor and working down, bleed radiators to release trapped air. After bleeding, re-check boiler pressure and top up again if needed. Trapped air can cause the pump to run dry/air-lock and trigger A1.

3. Reset the boiler: After correcting pressure or bleeding radiators, clear the fault by using the boiler’s reset procedure (many Worcester boilers require holding the reset or spanner button for a few seconds). Check if A1 returns.

4. Check for continuing pressure loss: If pressure drops again after topping up, find and repair leaks. Visible leaks should be reported to a plumber or Gas Safe engineer promptly.

5. Freeing a lightly seized pump (only non-invasive attempts): With the boiler switched off and isolated, some users report gently tapping the pump casing with a wooden handle to free a stuck rotor. Do not remove the pump cover or access internal parts unless you are qualified. If unsure or uncomfortable, stop and call an engineer.

Further diagnostics and when to stop DIY:

- If after topping up, bleeding and reset the A1 error persists, or if you hear grinding noises, the pump makes no sign of running, or the pump casing is abnormally hot, the pump is likely faulty (seized or bearing failure) or there is sludge/blockage. If sludge or magnetite is suspected (uneven radiator heating, black/brown water when draining), a system filter, chemical flush or powerflush may be required.

- If you find a puddle or continuing unexplained pressure loss, do not continue to operate the boiler — call a professional.

Call a professional if:

- The pump needs replacing or you need work inside the boiler casing.

- You cannot find or stop a leak or the pressure continues to fall after topping up.

- The A1 code persists after you have bled radiators and restored pressure.

- You detect sludge, require a system flush, or the pump shows signs of mechanical failure (grinding, vibration, hot casing).

What to tell the engineer:

- Model of boiler and exact error code (A1) and whether it is a persistent or intermittent fault.

- Current cold pressure reading and whether it falls after topping up.

- Whether you have found any visible leaks, whether you have bled radiators, and whether that changed anything.

- Any noises from the pump, and any other symptoms (no hot water, uneven radiator temperatures, water under the boiler).

Summary: start with safe basic checks — pressure, filling loop, look for leaks, bleed radiators, reset. If the fault remains, or if the pump appears seized, noisy or hot, or you need internal access or pump replacement, contact a Gas Safe registered engineer to diagnose and repair the boiler.