Low Information
P3 on Worcester Bosch Greenstar CDi Compact

Your boiler is currently running a self-cleaning routine to remove trapped air bubbles from the internal pipes and pump.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

Appliance is in Air purge mode, see service function 2.C.

What causes this fault?

This occurs when air becomes trapped within the boiler's heat exchanger or pump, often following a recent repair or system refill. The boiler automatically detects this air and triggers a programmed sequence to pulse the pump and vent the bubbles safely to ensure efficient operation. It isn't a mechanical failure, but rather a protective routine to prevent the system from overheating.

This code is more common in autumn when homeowners first switch their heating back on or bleed their radiators after a long period of disuse.

DIY fix possible

Wait for the timer to count down; the process usually takes 2 to 10 minutes.Ensure your radiator valves are open to help move air through the system.Check the pressure gauge is between 1 and 1.5 bar; top up if it has dropped.

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