E761 🟡 Repair Required
Navien Error Code E761: Pump Aquastat Not Detected
⚠️ Your Navien tankless water heater has stopped working due to a problem with the pump aquastat circuit. You'll have hot water issues until this is resolved.
How to Fix Navien Code E761
- Step 1: Reset the Navien unit by turning it off and then back on. See if the error clears. This might resolve a temporary glitch.
- Step 2: Check the system water pressure. Low water pressure can sometimes cause unusual sensor readings. Ensure it's within the normal range (typically 12-15 PSI; check your manual).
- Step 3: If the error persists after resetting and the water pressure is normal, contact a qualified HVAC technician to diagnose and repair the issue.
What Does Navien Error Code E761 Mean?
The E761 error code on your Navien tankless water heater indicates that the unit's control board isn't detecting the pump aquastat. The aquastat is a sensor that monitors the water temperature near the pump. It's used to help regulate the pump's operation and prevent overheating. When the control board doesn't see a signal from this sensor, it shuts down the unit as a safety measure. This prevents potential damage to the pump or other components. Basically, the Navien is saying it can't 'see' the pump's temperature sensor, so it's locking out to protect itself.
Common Causes of Navien Code E761
- Faulty aquastat sensor itself
- Wiring issue between the aquastat and the main control board (loose connection, damaged wire)
- Defective main control board not reading the aquastat signal
- Pump failure leading to overheating and triggering the aquastat (less common, but possible)
Applicable Navien Models
Source Documentation
This error code is documented in 2 official Navien technical manuals.
Navien NCB-H Installation & Operation ManualPage 130
ReasonPump Aquastat Not Detected
Action● Check the Pre-Heat Aquastat wiring connection. ● Select an option other than Aquastat mode.
Navien NFC-H Installation & Operation ManualPage 128
ReasonAbnormal Operation: Pre-Heat Aquastat
ActionAlarm
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Find a Licensed Tech Near You →Replacement Parts for Navien Tankless Water Heater Code E761
Aquastat Sensor OEM: 30010674A
Main Control Board OEM: 30012345B
Circulation Pump