Furnace displays F29, burner lights briefly then goes out, multiple attempts before lockout

Safety first: Only a qualified gas technician should work on burner and gas components.

• Check gas supply stability: A gas engineer should measure inlet pressure during operation to ensure it remains within Saunier Duval limits.
• Clean burner: Remove and clean the burner and injectors to remove dust, rust, or debris that can cause poor flame stability.
• Inspect ionization electrode: Clean or replace the electrode and ensure correct positioning in the flame.
• Flue inspection: Verify that the flue system is intact and not causing downdrafts or recirculation that could extinguish the flame.