Blocking High

Potterton Blocking Fault Code

Also written as BLOCKING — same fault.

The Potterton Blocking fault code means: your boiler has detected an issue with the air supply or internal startup signal, causing it to lock itself out for safety reasons.. It appears on 1 Potterton model 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: Mains Frequency incorrect or Air Switch Fault >1 min. or Reset button held in to force a restart (Green LED: ON, Red LED: FLASHING 2 Per Sec.)
Typical repair cost £120-250 (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 Blocking fault code

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

Source

Potterton Blocking 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 7 July 2026