Air Proving LOCKOUT High

Potterton Air Proving LOCKOUT Fault Code

Also written as AIRPROVINGLOCKOUT — same fault.

The Potterton Air Proving LOCKOUT fault code means: your boiler has stopped working because it cannot confirm that harmful exhaust gases are being safely cleared through the flue pipe.. It appears on 2 Potterton models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Manual Lockout. The APS (Air Pressure Switch) is not maintaining its signal. Has occurred 4 times while burner lit.

What causes the Potterton Air Proving LOCKOUT fault?

This fault occurs when the boiler's internal safety sensor cannot detect a steady flow of air through the system, meaning it isn't sure that exhaust fumes are leaving the house safely. The most common reasons are a failing fan that isn't spinning fast enough, a blockage in the flue pipe, or a perished rubber tube that has stopped the sensor from reading air pressure correctly.

This fault is more common during periods of high winds, which can create back-pressure in the flue and interfere with the air pressure sensor's readings.

Typical repair cost £120-280 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Potterton models that show the Air Proving LOCKOUT fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Potterton Air Proving LOCKOUT 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