E736 🟡 Repair Required
Navien Error Code E736: CH Return Thermistor Failure
⚠️ Your Navien boiler has detected a potential issue with the return water temperature sensor. It's safe to continue using other appliances, but this issue requires professional attention.
How to Fix Navien Code E736
- Check if your boiler is still heating your home. If it is, you can continue using it until a professional can repair it.
- Turn off your boiler if it's not heating your home or if you're not comfortable using it.
- Contact a licensed HVAC technician to diagnose and repair the issue. Do not attempt to repair this yourself.
What Does Navien Error Code E736 Mean?
The E736 error on your Navien boiler indicates a failure in the return water temperature thermistor. This sensor measures the temperature of the water returning from your heating system. If it's not working correctly, your boiler can't accurately control the water temperature, leading to inefficient heating and potential system damage. This error is typically caused by a faulty thermistor, but it could also be due to a wiring issue or a problem with the boiler's control board.
Common Causes of Navien Code E736
- Faulty return water temperature thermistor
- Wiring issue between the thermistor and the control board
- Problem with the boiler's control board
Applicable Navien Models
Source Documentation
This error code is documented in 5 official Navien technical manuals.
NFB-H Installation & Operation ManualPage 116
ReasonCascade Communication
ActionCheck cascade cable.
Navien NCB-H Installation & Operation ManualPage 130
ReasonCascade Communication
ActionContact technical support at 1-800-519-8794.
Navien NFB-H Installation & Operation ManualPage 116
ReasonCascade Communication
ActionCheck cascade cable.
Navien NFC-H Installation & Operation ManualPage 128
ReasonAbnormal operation: cascade communication
ActionAlarm
Navien NHB-H Installation & Operation ManualPage 119
ReasonCascade Communication
ActionCheck cascade cable.
Need a Pro to Fix Navien Code E736?
A licensed HVAC technician can diagnose and fix this issue quickly.
Find a Licensed Tech Near You →Replacement Parts for Navien Tankless Water Heater Code E736
Return Water Temperature Thermistor OEM: 7100000003