How much does it cost to fix Main error code 1 flash green?

Typical repair cost for the Main 1 flash green fault is £150-300 including labour.

1 flash green High

Main 1 flash green Fault Code

Q: What does the Main 1 flash green fault code mean?

Your boiler has shut down because the water inside is getting too hot, too quickly, or cannot circulate properly through your heating system.

Also written as 1FLASHGREEN — same fault.

The Main 1 flash green fault code means: your boiler has shut down because the water inside is getting too hot, too quickly, or cannot circulate properly through your heating system.. It appears on 1 Main model in our database.

Technical description: Temperature protection: Maximum flow temperature exceeded, Flow temperature rise rate too high, Excessive difference between flow and return temperature

Typical repair cost £150-300 (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 1 flash green fault code

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

Insul 7 Repair: £150-300

Source

Main 1 flash green 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