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Sensor fault: tankless water heater / continuous flow hot water system codes by brand
A sensor, probe or detection circuit (other than a temperature or pressure sensor) is giving no or implausible readings.
| Brand | Code | Meaning | What you can do |
|---|---|---|---|
| Rinnai | 25 | Sensor fault or condensate blockage (depends on model) | Depends on your model |
| Rinnai | 72 | Flame rod circuit error | Call a pro |
| Rinnai | 73 | Burner thermocouple fault | Call a pro |
| Navien | E004 | False flame detected | Safe checks first, then a pro |
| Navien | E439 | Flow sensor fault | Call a pro |
| Navien | E785 | Flow switch or sensor fault | Call a pro |