133 High

Main 133 Fault Code

The Main 133 fault code means: your boiler has stopped working because it cannot light its internal flame to heat your water or radiators.. It appears on 1 Main 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: Gas supply interrupted, ignition failed or flame not detected
Typical repair cost £120-250 (including labour)

Engineer required

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

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Main models that show the 133 fault code

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

Source

Main 133 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