73
Rinnai
Parameter Setting or Communication Error
Boiler shows error 73; may occur after replacing the control board or changing settings.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Incorrect DIP switch or jumper settings, Mismatched PCB and boiler model, Corrupted configuration data, Faulty communication between sub-PCBs
How to Fix / Troubleshooting
Safety first: Turn off power before adjusting any internal switches.
- Verify DIP switch settings: Compare the DIP switch positions on the new PCB with the original board or the installation manual for your specific Rinnai boiler model.
- Check model compatibility: Ensure the replacement PCB is approved for your exact boiler model and gas type.
- Inspect communication cables: If your boiler uses multiple boards (e.g., display PCB, main PCB), confirm that all communication harnesses are connected correctly.
- Factory reset (technician only): Some models allow a parameter reset procedure that should be performed by a trained technician.
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Repair Difficulty
Hard
4/5
Required Part
Main Control PCB
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