What does the Heatline F4 fault code mean?

Your boiler has stopped working because it failed to light a flame or the drainage pipe for waste water is blocked.

How much does it cost to fix Heatline error code F4?

Typical repair cost for the Heatline F4 fault is £90-280 including labour.

Check if your gas supply is active (e.g., check other gas appliances or your meter credit).

Lockout due to ignition problem or Condensate Trap Blockage

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Lockout fault with a reset-needed pattern.

Older boilers — thermocouple, draught, gas supply.

Safety-critical — turn off, read this.