A8 alarm, outdoor temperature reading missing or unrealistic, system may run incorrectly

Safety: Turn off power before working on sensor wiring.

• Check sensor location: The Nibe outdoor sensor should be mounted on a shaded north or northwest wall, away from direct sun and heat sources. If incorrectly placed, relocate according to Nibe guidelines.
• Inspect sensor body and cable: Look for physical damage, water ingress, or chewed cable. Repair or replace damaged cable runs.
• Verify terminal connections: At the Nibe control board, tighten the outdoor sensor terminals and ensure the wires are correctly landed.
• Reset alarm: Restore power and clear the A8 alarm. Compare the displayed outdoor temperature with an accurate thermometer; if it is far off, replace the sensor.