BoilerFaultCodesPotterton On Off On Off * * On On Fault Code
Also written as ONOFFONOFFONON — same fault.
The Potterton On Off On Off * * On On fault code means: your boiler has shut down because it is unable to drain away the waste water it produces, causing a small internal reservoir to overflow.. It appears on 1 Potterton model in our database.
Technical description: Condensate pump over level switch activated - reservoir level too high resulting in ignition lockout.
What causes the Potterton On Off On Off * * On On fault?
This fault occurs when the boiler's internal drainage system becomes blocked, preventing the waste water produced during heating from leaving the unit. The most common reason is a buildup of debris in the condensate trap or a failure of the mechanical pump that pushes the water away. To prevent internal flooding and damage, a safety switch triggers and shuts the boiler down until the water level drops.
This fault is more common in winter, as the external pipe that carries the waste water away can freeze, causing water to back up into the boiler.
DIY fix possible
Locate the external white plastic drainage pipe and check if it has frozen or is blocked with debris.If frozen, gently pour warm (not boiling) water over the pipe to melt the ice block.Check that the condensate pump (if fitted) is plugged in and switched on.
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Gas Safe Register →Potterton models that show the On Off On Off * * On On fault code
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Source
Potterton On Off On Off * * On On 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