E07 displayed, unit may run briefly then shut down; return temperature reading appears incorrect.

Safety: Disconnect power before working inside the appliance.

• 1. Locate return sensor: The return NTC sensor is usually mounted on the return water connection or lower manifold of the Triangle Tube water heater.
• 2. Inspect harness: Follow the sensor wires back to the control board. Look for pinched, cut, or overheated wiring. Reseat the connector at both ends.
• 3. Check for moisture: If the sensor is in a well or pocket, check for leaks or condensation. Dry the area and correct any leaks.
• 4. Test sensor (optional): With the sensor unplugged and power off, measure resistance and compare to the manufacturer’s chart. Replace if open, shorted, or far out of range.
• 5. Replace sensor: Install a new OEM return NTC sensor if needed. Ensure it is fully inserted and secured.
• 6. Power up and verify: Restore power, clear the error, and confirm that supply and return temperatures are plausible and that the unit runs without re-triggering E07.