Visible rust or corrosion inside the heater cabinet; components appear deteriorated.

Safety first: Turn off power and gas before inspection.

• Address leaks: Repair any plumbing or internal leaks contributing to moisture inside the cabinet.
• Ventilation: Ensure the heater has proper clearances and is not enclosed in a corrosive environment (e.g., chemical storage room).
• Clean and protect: Light surface rust can be brushed off and treated with a rust-inhibiting paint on non-critical surfaces.
• Replace compromised parts: Severely corroded burners, manifolds, or heat exchangers should be replaced. If structural components are compromised, consider replacing the heater.