E786 🟡 Repair Required
Navien Error Code E786: Header Thermistor Failure
⚠️ Your Navien boiler has detected a header thermistor failure, which could lead to system damage if not addressed promptly.
How to Fix Navien Code E786
- Step 1: Turn off your boiler at the main power switch to prevent further operation until the issue is resolved.
- Step 2: Inspect the wiring harness connected to the header thermistor for any signs of damage or corrosion.
- Step 3: If you're comfortable doing so, check the thermistor's resistance using a multimeter. A faulty thermistor will typically read either extremely high or low. If you're unsure about any of these steps, contact a professional HVAC technician.
What Does Navien Error Code E786 Mean?
The E786 error on your Navien boiler indicates a failure in the header thermistor, a sensor that monitors the temperature of the boiler's water jacket. This error is typically caused by a faulty thermistor or a poor electrical connection. If ignored, it could lead to overheating and potential damage to your boiler.
Common Causes of Navien Code E786
- Faulty header thermistor
- Poor electrical connection at the thermistor
- Corrosion or damage to the thermistor's wiring
Applicable Navien Models
Source Documentation
This error code is documented in 6 official Navien technical manuals.
NFB-H Installation & Operation ManualPage 116
ReasonImproper Front Panel Detected
ActionCheck for correct panel version.
Navien NFC-H Installation & Operation ManualPage 128
ReasonImproper front panel
ActionAlarm
Navien NCB-H Installation & Operation ManualPage 130
ReasonImproper Front Panel
ActionContact technical support at 1-800-519-8794.
Navien NFB-H Installation & Operation ManualPage 116
ReasonImproper Front Panel Detected
ActionCheck for correct panel version.
Navien NHB-H Installation & Operation ManualPage 119
ReasonImproper Front Panel Detected
ActionCheck for correct panel version.
Navien NPF Installation & Operation ManualPage 128
ReasonAbnormal front control panel connection
ActionThis error occurs when a different type of a front control panel is connected to the furnace. ● Check if the front control panel connected to the furnace is appropriate for the NPF Series furnace.
Need a Pro to Fix Navien Code E786?
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Find a Licensed Tech Near You →Replacement Parts for Navien Tankless Water Heater Code E786
Header Thermistor OEM: 9015110000