BoilerFaultCodesPotterton On Off On Off Fault Code
Also written as ONOFFONOFF — same fault.
The Potterton On Off On Off fault code means: your boiler has shut down because water intended for your drain is backing up and has triggered a safety sensor.. It appears on 1 Potterton model in our database.
Technical description: Condensate pump level switch activated for longer than 3 minutes - boiler locks out.
What causes the Potterton On Off On Off fault?
This fault occurs when the internal tank that collects waste water becomes full and cannot empty itself properly. The most common reasons are a mechanical failure of the condensate pump or a blockage in the thin plastic discharge pipe leading away from the boiler. To prevent an internal flood, a safety sensor triggers and shuts the system down until the water level drops.
This fault is particularly common during freezing winter temperatures, as the external portion of the waste pipe can freeze solid and prevent water from leaving the pump.
DIY fix possible
Check if the condensate pump is plugged in and turned on at the wall.Inspect the thin plastic pipe leading from the pump for any kinks or blockages.If the weather is freezing, check if the external waste pipe is frozen and thaw it with warm (not boiling) water.
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Source
Potterton On Off On Off fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026