F25 Safety switch-off — Thermal link interruption

What does F25 mean?

The boiler has safely shut off due to an interruption in the thermal link stat, located at the top of the main heat exchanger. This can be caused by a break in the cable harness or a blocked flue.

• Interruption to thermal link stat (top of main heat exchanger)
• Break in cable harness
• Blocked flue run
• Combustion issues
• NTCs and Harness issues (MK1)

Click steps to track your progress.

1. 1

   Check the thermal link for continuity (requires specialist tools).

2. 2

   Check the cable harness for continuity (requires specialist tools).

3. 3

   Ensure the flue run is not blocked.

4. 4

   Verify that combustion is operating correctly (requires specialist tools/knowledge).