Navien E007 Error Code — What It Means
The E007 error on your Navien tankless water heater means the hot water outlet thermistor circuit is open. In simple terms, the control board cannot see a valid electrical signal from the temperature sensor on the outgoing hot-water line. This sensor tells the unit how hot the water leaving the heater is, so when the circuit is open the heater locks out to protect itself. An open circuit usually points to a failed thermistor, broken wiring, or a loose connector rather than a minor calibration issue.
Common Causes
- Failed outlet thermistor The sensor itself has failed internally and no longer completes the circuit.
- Loose or disconnected wiring The harness plug at the thermistor or control board has worked loose or come unplugged.
- Damaged wiring or connector pins Wires have been pinched, cut, or corroded, or connector pins are bent or corroded, breaking continuity.
- Harness abrasion or rodent damage The thermistor wiring has rubbed through insulation or been chewed, creating an open circuit.
- Control board interpretation fault The board itself is no longer reading a good sensor correctly, though this is much less common than sensor or wiring failure.
Step-by-Step Fix
- Verify the error code on the display panel and confirm the unit is showing E007, not a similar sensor fault.
- Turn off power to the water heater at the breaker or disconnect switch, then wait 30 seconds before opening the cabinet.
- Inspect the outlet thermistor connector on the hot-water outlet pipe and at the control board for looseness, corrosion, bent pins, or obvious damage, and reseat both ends firmly.
- Check thermistor continuity with a multimeter set to ohms by unplugging the sensor and measuring across its terminals; an open or infinite reading confirms a failed thermistor, while a finite resistance suggests the sensor may be good.
- Trace the wiring from the thermistor to the board, looking for pinched, cut, or abraded insulation, and repair any breaks with proper splice connectors or replace the harness.
- Replace the hot water outlet thermistor if the sensor tests open or if the wiring is intact but the code persists, following the manufacturer’s service instructions for your model.
- Restore power and test the unit for normal operation, watching the display to confirm the E007 clears and the outlet temperature reads correctly.
Parts Often Needed
| Part | Notes |
|---|---|
| Navien hot water outlet thermistor | Amazon | Match your model number; this is the primary failure point for E007. |
| Thermistor wiring harness | Amazon | Order if the connector or wires are damaged beyond a simple splice repair. |
| Control board / PCB | Amazon | Only if the sensor and wiring test good but the fault remains; verify with a technician first. |
When to Call a Pro
Call a licensed plumber or Navien service technician if you are not comfortable working with 120-volt power, do not own a multimeter, or cannot locate the outlet thermistor on your unit. Also call if you replace the sensor and repair all wiring but E007 returns, since that points to a control-board issue that requires factory training and genuine parts. Navien recommends having your serial number ready when you contact support so the technician can pull the correct service data for your specific model.