29 High

Main 29 Fault Code

The Main 29 fault code means: your boiler has detected a problem with the sensor that monitors the temperature for your radiators, causing the heating to stop working.. It appears on 2 Main 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: Fault on Central Heating Sensor
Typical repair cost £90-160 (including labour)

Engineer required

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

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Main models that show the 29 fault code

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

Source

Main 29 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026