H7 displayed; unit may still operate but with reduced performance or noisy combustion.

Safety: Turn off power and gas before cleaning combustion components.

• Clean burner surface: Remove the burner assembly if accessible. Use a soft brush and vacuum to remove dust and light soot. Do not enlarge burner ports.
• Inspect heat exchanger: Look for heavy soot or corrosion. Light dust can be vacuumed; heavy deposits require professional cleaning.
• Check flue terminal: Ensure the terminal is clear and the flue joints are intact.
• Schedule service: H7 often indicates the unit is due for a full Junkers service (combustion analysis, gasket replacement, etc.).