Rinnai continuous flow water heaters have a self diagnostic capability. If a fault occurs, an error code will flash on the digital monitor of your water controllers. This assists with diagnosing the fault, and may enable you to overcome a problem without a service call. Please quote the code displayed when enquiring about service.
You may be able to clear the error code simply by turning the hot water tap OFF, then ON again. If this does not clear the error code, try pushing the On/Off button OFF, then ON again, or turning the power for unit OFF, waiting 10 seconds and then ON again.
If the error code still remains, contact Rinnai for advice.