Boiler shows E16 and indicates outdoor sensor error on the display

Safety: Turn off power before working on wiring.

• Locate outdoor sensor: The Dettson outdoor sensor is typically mounted on an exterior north or northwest wall, away from direct sun.
• Inspect cable: Follow the sensor cable back to the boiler. Look for cuts, staples through the wire, or UV damage.
• Check connections: Reseat the sensor wires at the boiler control terminals, ensuring correct polarity if required.
• Sensor test: A technician can measure resistance at the sensor and compare to Dettson's temperature/resistance chart. Replace the sensor if out of range.
• Control board: If a known-good sensor still triggers E16, the outdoor sensor input on the control board may be defective.