P3 error, furnace output limited, may not reach set temperature

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

Steps:

• Locate sensor: The Buderus outdoor sensor is usually mounted on a north or northwest exterior wall, away from direct sun and heat sources.
• Inspect cable: Check for damage from weather, animals, or fasteners. Repair or replace damaged sections.
• Check connections: Ensure the sensor wires are firmly connected to the designated terminals on the Buderus control.
• Resistance test: With power off, measure sensor resistance and compare to Buderus outdoor sensor charts.

If the sensor is defective, replace it with the correct Buderus outdoor sensor model.