Safety: Turn off power and let the boiler cool before working on sensors.

Step 1 – Locate return sensor: Find the NTC sensor on the return pipe entering the Triangle Tube boiler. It may be clipped to the pipe or inserted into a well.
Step 2 – Inspect and reseat: Check that the sensor is firmly attached and making good contact with the pipe. Reseat the electrical connector at both the sensor and the control board.
Step 3 – Visual check for damage: Look for crushed cable, cuts, or signs of overheating on the sensor body.
Step 4 – Reset and test: Restore power and reset the boiler. If E07 persists, the sensor is likely defective.
Sensor replacement: Replace the return NTC with an OEM Triangle Tube sensor, ensuring proper sealing if it is a wet sensor. Bleed air from the system if water was lost.
Professional help: If a new sensor does not resolve the issue, a technician should test resistance values and the control board.

Boiler displays E07, return temperature reading is invalid

Possible Causes