Boiler shows E06; burner shuts down; may be accompanied by very hot supply temperature

Safety: Turn off power and allow the boiler to cool before touching any sensors or piping.

• Locate supply sensor: On NTI boilers, the supply NTC is typically clipped or inserted into a sensor well on the outlet manifold or heat exchanger.
• Check connection: Inspect the two‑wire plug for corrosion, loose pins, or broken wires. Reseat the connector firmly.
• Test resistance: With power off, disconnect the sensor and measure resistance with a multimeter. Compare to the NTI temperature/resistance chart. If reading is open, shorted, or far off spec, replace the sensor.
• Inspect mounting: Ensure the sensor is fully inserted into the well and has good thermal contact. Re‑clip or secure as needed.
• Control board check: If a known‑good sensor still gives E06, the control board’s sensor circuit may be defective and should be evaluated by a technician.