Water heater stops during operation and displays Code 03; unit may restart after some time
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.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn OFF power at the breaker before opening the unit. Do not work on live electrical circuits.
Steps to check:
- Check household power: Confirm the circuit breaker feeding the Rinnai water heater is not tripped. Reset if necessary. If it trips repeatedly, stop and call an electrician or technician.
- Inspect power cord and outlet (if corded): Ensure the plug is fully seated and the outlet is not loose or damaged. Test the outlet with another appliance.
- Check internal connections: With power OFF, remove the front cover and inspect the power terminal block for loose screws or burned wiring. Tighten loose terminals gently.
- Reset the unit: Restore power and press ON/OFF to reset. Run hot water and monitor for recurrence.
When to call a professional: If Code 03 recurs and household power is stable, the control board or internal wiring may be defective and should be diagnosed by a qualified technician.
Repair Difficulty
Required Part
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