Fault F3 (Detailed 139) — Burner fault: flame signal already present at start

What does F3 mean?

The burner is in fault mode because a flame signal was already detected when the burner attempted to start. This is a safety mechanism to prevent gas ignition if a flame is falsely detected, indicating a potential sensor issue.

• Flame signal already present at burner start

Click steps to track your progress.

1. 1

   Check the ionization electrode and its connecting cable for any faults, contamination, or incorrect installation.

2. 2

   Ensure all wiring related to the flame detection system is secure and undamaged.

3. 3

   Press the reset button R on your boiler.

4. 4

   If the problem persists, a qualified technician should investigate the ionization electrode or control unit.