Navien Water Heater Error Code 038: How to Fix It

Medium 30-60 minutes Medium Severity Verified June 2026
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Error Code
038
Brand
Navien
Product Type
water_heater
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
30-60 minutes
Error code 038 on your Navien water heater indicates a return thermistor fault. This means the sensor that monitors the water temperature returning to the boiler is malfunctioning or has failed. Your unit may shut down to prevent overheating or damage.
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Tools You'll Need

How to Fix Error Code 038

  1. Power Down the Unit

    Always disconnect power and gas before servicing to prevent electrical shock or gas leaks.

  2. Locate the Return Thermistor

  3. Check Wiring Connections

  4. Test the Thermistor with a Multimeter

    Ensure the multimeter leads are on the correct ports to avoid damage.

  5. Replace the Return Thermistor

    Use only genuine Navien parts for compatibility and safety.

  6. Reset and Restart

    If the error persists after replacement, contact a professional.

Parts You May Need

Return thermistor (NTC sensor)
Check Price on Amazon
Return thermistor (NTC sensor)
Check Price on Amazon
Return thermistor (NTC sensor)
Check Price on Amazon
Return thermistor (NTC sensor)
Check Price on Amazon
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When to Call a Professional

If replacing the thermistor does not clear the error, or if the control board appears damaged, call a qualified HVAC technician. For gas line or combustion issues, always consult a professional.

Frequently Asked Questions

What does Navien error code 038 mean?
Error code 038 indicates a return thermistor fault. The sensor reading the water temperature returning to the heater is malfunctioning.
Can I still use my Navien water heater with error 038?
No, the unit will typically shut down to prevent damage. You should repair the thermistor before resuming operation.
How do I test the return thermistor on my Navien?
Use a multimeter set to resistance. Disconnect the thermistor and measure between its two wires. Room temperature should give about 10,000 ohms. If open or shorted, replace it.
Is error 038 common on Navien units?
Yes, thermistor failures can occur over time due to heat cycling. It's a known issue but not extremely common.
Where can I buy a Navien return thermistor?
You can order from Navien authorized dealers or online retailers. Search for your model number plus 'return thermistor'.

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