Boiler displays E13: outdoor temperature sensor reading is invalid.

Safety: Turn off the power before working on low-voltage wiring.

• Step 1 – Locate outdoor sensor: Locate the Triangle Tube outdoor sensor mounted on an exterior wall, typically on the north or shaded side.
• Step 2 – Inspect wiring: Inspect the two-conductor cable from the sensor back to the boiler. Look for cuts, staples through the wire, or corrosion at the terminals. Reseat the wires at the control board.
• Step 3 – Sensor placement: Ensure the sensor is not in direct sunlight, above a dryer vent, or near other heat sources that can skew readings.
• Step 4 – Reset boiler: Restore power and see if E13 clears. If not, the sensor may be defective.
• Replace sensor: Install a new Triangle Tube-compatible outdoor sensor and reconnect the wires with correct polarity (if specified).
• Technician help: If the error persists, the control board may need to be tested and replaced by a professional.