Navien Error Code E046: Outlet Thermistor Open/Short
How to Fix Navien Code E046
- Step 1: Turn off power to the Navien unit at the wall switch or breaker. Wait 30 seconds, then turn it back on. If the error clears, it was a temporary glitch.
- Step 2: Check that the unit's front panel is properly closed and all wire connections inside are snug. Do not remove the panel if you are not comfortable.
- Step 3: If the error returns, call a Navien-qualified technician. They will need to test the thermistor resistance and likely replace it.
How to Reset Navien Code E046
- Turn off the unit using the power button on the front panel.
- Turn off the gas supply valve.
- Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
- Restore power at the breaker, then open the gas valve.
- Turn the unit back on. If the error returns, the underlying issue needs repair.
What does E046 mean?
The E046 code on your Navien unit means the outlet thermistor, a temperature sensor located on the hot water outlet pipe, is either open (infinite resistance) or shorted (near-zero resistance). This sensor tells the control board how hot the water leaving the heat exchanger is. When it fails, the board can't regulate the burner properly, so it shuts down the system to prevent overheating or damage. This is a common issue on Navien combi boilers and water heaters, especially after several years of use.
For a homeowner, you'll likely see this error after the unit runs for a minute or two and then stops. The display will flash E046, and the unit will not heat water or run the central heating until it's fixed. The thermistor is a sensor mounted on the outlet pipe, often behind the front panel. While no gas or water leaks are associated with this code, you need a professional to replace the sensor to get your system back online.
The fix requires removing the front cover, unclipping the sensor from the pipe, and installing a new one. Most homeowners should call a pro, but if you're handy, you can buy the right thermistor from a Navien supplier. Just be aware that mishandling the wiring can cause other issues.
Affected Models
- NCB-H
- NFB-H
- NFC-H
- NHB-H
- NHW-A
- NPE-A2
- NCB
- NCB
- NCB
- NPE
- NPE
- NPE
- NHB
- NHB
- NCB
- NCB
- NPE
- NPE
- NCB
- NCB
- NPE
- NCB
- NPE
- NHB
- NCB
- NPE
- NPE
- NCB
- NCB
- NPE
- NPE
- NPE
- NPE
- NHB
- NHB
- NCB
- NCB
- NPE
- NPE
- NBP
- NPE
- NPE
- NPE
- NFC
- NFC
- NCB
- NPE
- NPE
- NPE
- NCB
- NPE
- NCB
- NPE
- NPE
- NCB
- NPE
- NHB
- NPE-S
- NPN
- NPN
- NCB
- NPE
- NCB
- NPE
- NHB
- NPB
- NFC
- NFC
- NHB
- NPF
- NPF
- NPE
- NHB
Source Documentation
| Manual | Page | Reason | Action |
|---|---|---|---|
| NFB-H Installation & Operation Manual | 116 | Heat Exchanger Thermistor | Check thermistor connector. |
| Navien NCB-H Installation & Operation Manual | 129 | Heat Exchanger Thermistor | Contact technical support at 1-800-519-8794. |
| Navien NFB-H Installation & Operation Manual | 116 | Heat Exchanger Thermistor | Check thermistor connector. |
| Navien NFC-H Installation & Operation Manual | 127 | Abnormal operation: heat exchanger overheating sensor | Auto RESET |
| Navien NHB-H Installation & Operation Manual | 119 | Heat Exchanger Thermistor | Check thermistor connector. |
| Navien NPF Installation & Operation Manual | 125 | Abnormal limit control operation on the heat exchanger | This error occurs when the limit control on the heat exchanger does not operate properly. ● Stop operating the furnace and contact Technical Support at 1-800-519-8794. |
Replacement Parts
| Part | OEM Number | Est. Cost |
|---|---|---|
| Outlet Thermistor (NTC sensor) | 30019717A | — |
| Inlet Thermistor (if misdiagnosed) | 30019718A | — |
| Control Board (PCB) | — | — |
Related Codes on Same Models
| Code | Description | Severity |
|---|---|---|
| E001 | Ignition Failure | Warning |
| E003 | Abnormal Ignition | Warning |
| E004 | False Flame Detection | Warning |
| E012 | Flame Loss | Warning |
| E016 | Overheating | Warning |
| E030 | Exhaust Overheat Sensor | Warning |
| E031 | Inlet Thermistor Open/Short | Warning |
| E047 | DHW Thermistor Open/Short | Warning |
| E060 | Fan Motor Abnormality | Warning |
| E109 | Fan Motor Speed Low | Warning |