Error code
Worcester Bosch Boiler Fault Code A1
Quick answer
A1
Water circulation or pump performance issue
First safe action
Check the boiler pressure and any obvious user controls described in the manual.
Meaning
Worcester Bosch boiler fault code A1 usually points to poor water circulation through the boiler or heating system, often involving the pump, trapped air, or a blockage.
Likely causes
- Pump issue
- Restricted circulation through the system
- Airlock or sensor reading linked to poor flow
Safe first checks
- Check the boiler pressure and any obvious user controls described in the manual.
- Do not dismantle pumps, valves, or pipework yourself.
- Use a standard reset only if the manufacturer guidance allows it.
How to reset
- Try a single user reset after any permitted checks are completed.
- Arrange an engineer if circulation-related faults return.
When to call an engineer
If circulation faults return, book a qualified heating engineer rather than continuing to reset the boiler.
Safety warning
Do not open the casing or interfere with pumps, valves, or sealed system components.
Useful hub links
Related fault codes
268 for Worcester Bosch Boiler
Water circulation or pump performance issue
286 for Worcester Bosch Boiler
Water circulation or pump performance issue
C6 for Worcester Bosch Boiler
Fan, flue, or air pressure sensing problem
EA for Worcester Bosch Boiler
The boiler has failed to ignite properly
295 for Worcester Bosch Boiler
A boiler sensor is giving an invalid reading
296 for Worcester Bosch Boiler
Flame detection has been lost during operation
Relevant guides
Frequently asked questions
Can I keep resetting a Worcester Bosch boiler with A1?+
No. If A1 returns after one standard user reset, stop there and arrange a qualified engineer if the manual gives no safe next step.
Is A1 something I can repair myself?+
Boiler faults should be treated cautiously. Stay within the user checks in the manual, and leave gas, combustion, and internal boiler repairs to a qualified professional.