Error code 51 displayed; unit may not respond correctly to remote controller commands.

Safety first: Turn OFF power to the heater before working on wiring.

Steps to check and correct:

• Inspect remote cable: Follow the cable from the Noritz remote controller to the heater. Look for cuts, staples through the cable, or crushed sections. Replace damaged cable.
• Verify wiring polarity: Noritz remotes are polarity-sensitive. Confirm that the + and - terminals are wired correctly at both the remote and heater per the installation manual.
• Reseat connectors: Remove and reconnect the remote cable at the PCB terminal block to ensure a solid connection.
• Test with another remote: If available, connect a known-good Noritz remote to rule out a defective controller.
• Reset and test: Restore power. If error 51 persists, the PCB communication circuit may be faulty and require replacement.