Navien Error Code E031: Inlet Thermistor Open/Short
Warning: Your Navien boiler has detected an issue with the inlet thermistor and has shut down to prevent damage. Call a professional for repair.
How to Fix Navien Code E031
- Check if the boiler's power is turned off at the main circuit breaker
- Inspect the wiring harness and connections for any visible damage or corrosion
- Contact a licensed HVAC technician for a thorough inspection and repair
How to Reset Navien Code E031
- 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.
Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.
What Does Navien Error Code E031 Mean?
The E031 error on your Navien boiler indicates an open or short circuit in the inlet thermistor. This component measures the temperature of the water entering your boiler. When it's not functioning correctly, your boiler can't accurately monitor the water temperature, leading to system lockouts. This error is common in Navien boilers due to their advanced temperature control systems.
Common Causes
- Wiring issues or damage to the inlet thermistor
- Corrosion or mineral buildup on the thermistor
- Faulty control board or wiring harness
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| Boiler is not heating | Measure the resistance of the inlet thermistor using a multimeter | Resistance should be within the manufacturer's specified range (typically between 10,000 to 100,000 ohms) |
| Thermistor resistance is out of range | Inspect the thermistor and its wiring for any visible damage or corrosion | No visible damage or corrosion |
Applicable Navien Models
Source Documentation
Referenced in 5 official Navien technical manuals.
| Manual | Page | Reason | Action |
|---|---|---|---|
| NFB-H Installation & Operation Manual | 116 | Burner Overheat | Check burner temperature fuse. |
| Navien NCB-H Installation & Operation Manual | 129 | Burner Overheat | Contact technical support at 1-800-519-8794. |
| Navien NFB-H Installation & Operation Manual | 116 | Burner Overheat | Check burner temperature fuse. |
| Navien NFC-H Installation & Operation Manual | 127 | Overheating of burner | Manual RESET |
| Navien NPF Installation & Operation Manual | 125 | Overheating of the burner | This error occurs when the overheat controller on the burner is initiated during combustion due to the burner overheating. ● If the furnace is continuously inoperable, contact Technical Support at 1-800-519-8794. |
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Inlet Thermistor | 4010000001 | — | Find Part |
| Control Board | 4010000002 | — | Find Part |
Related Codes on Same Models
Other codes that affect the same Navien model families as E031.
| 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 |
| E046 | Outlet Thermistor Open/Short | Warning |
| E047 | DHW Thermistor Open/Short | Warning |
| E060 | Fan Motor Abnormality | Warning |
| E109 | Fan Motor Speed Low | Warning |