How much does it cost to fix Main error code 4 flashes red?

Typical repair cost for the Main 4 flashes red fault is £180-350 including labour.

4 flashes red High

Main 4 flashes red Fault Code

Q: What does the Main 4 flashes red fault code mean?

Your boiler is having trouble breathing because a part responsible for moving air and fumes is not working correctly, which has caused it to shut down for safety.

Also written as 4FLASHESRED — same fault.

The Main 4 flashes red fault code means: your boiler is having trouble breathing because a part responsible for moving air and fumes is not working correctly, which has caused it to shut down for safety.. It appears on 1 Main model in our database.

Technical description: Fan fault (Fan calibration error, Fan failure)

Typical repair cost £180-350 (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 4 flashes red fault code

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

Insul 7 Repair: £180-350

Source

Main 4 flashes red 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