E50 error, unit may lock out; often related to safety chain or multiple sensor faults.

Safety: Do not bypass safety devices. Isolate power and gas.

• Check all safety thermostats: Inspect overheat and flue stats for manual reset buttons and press once if tripped. Investigate why they tripped.
• Inspect wiring harness: Follow the safety loop wiring between thermostats and PCB. Repair any damaged or loose connections.
• Look for overheating signs: Soot, discoloration, or melted insulation indicate serious overheating that must be corrected before resetting.
• Professional diagnosis: If E50 persists, a technician should trace the safety circuit with a wiring diagram.