How to Fix Worcester Bosch A1-281 Fault Code (UK)
Worcester Bosch showing A1-281 — Pump run-on. UK diagnosis, likely spare (boiler pump) and step-by-step reset.
What the code means
A1-281 on a Worcester Bosch indicates pump run-on. The boiler locks out to protect the heat exchanger and, on gas faults, to comply with the Gas Safety (Installation and Use) Regulations. Always reset to confirm the code is live, not historical.
Likely spare
The most common fix is the boiler pump. Check the exploded diagram against the GC number on the data plate before ordering — Worcester Bosch revised parts on Worcester Bosch units mid-production.
Fix procedure
Bleed air from AAV, check PWM signal, replace pump head.
Log the fault and reset. If the code returns within 24 hours, escalate to full electrical diagnosis with a manometer and multimeter.
Frequently asked questions
- Can I reset A1-281 myself?
- You can press the reset button up to 3 times. If A1-281 returns, the boiler needs a Gas Safe engineer — it is illegal to repair gas components without registration.
- Is the part covered under warranty?
- Worcester Bosch standard warranty is 2–10 years depending on model. Registered installations get the full term. Check the sticker inside the case.
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