Navien Error Code E438: Navien Error Code E438 - Abnormal Operation
Warning: Your Navien tankless water heater or combi-boiler has detected an abnormal operation and has likely locked out. This requires investigation to restore hot water and/or heating.
How to Fix Navien Code E438
- Step 1: Reset the unit by turning off the power switch for 5 minutes, then turn it back on. See if the error clears.
- Step 2: Check the incoming water pressure to the unit. Ensure it meets the minimum requirement specified in your Navien manual.
- Step 3: Inspect the exterior vent for any obvious obstructions like leaves, snow, or debris. Clear any blockages you can safely reach.
- Step 4: If the error persists after these steps, contact a qualified HVAC technician to diagnose and repair the unit.
How to Reset Navien Code E438
- 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 E438 mean?
The Navien error code E438 indicates that the unit has detected an abnormal operation. This is a broad error code that essentially means the unit's control board has sensed something is not right during its normal operation. It could be related to combustion, water flow, or other sensor readings falling outside acceptable parameters. The unit will likely shut down as a safety measure. This code is often triggered by a temporary issue but can also point to a more serious underlying problem that needs professional attention. Because this is a broad error, further diagnostics are needed to pinpoint the root cause.
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
Replacement Parts
| Part | OEM Number | Est. Cost |
|---|---|---|
| Air Pressure Switch (APS) | 30010687A | — |
| Flow Sensor | 30011812A | — |
| Gas Valve | — | — |
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 |
| E046 | Outlet Thermistor Open/Short | Warning |
| E047 | DHW Thermistor Open/Short | Warning |
| E060 | Fan Motor Abnormality | Warning |