Furnace shows outdoor sensor error; weather-compensated control not functioning correctly.

Safety: Turn off power before working on wiring.

• Locate outdoor sensor: Find the IVT outdoor temperature sensor on an exterior wall, typically on the north or shaded side.
• Inspect housing: Check for physical damage, cracked casing, or signs of water ingress. Ensure the sensor is not in direct sunlight or near exhaust vents.
• Check cable: Follow the cable back into the building as far as accessible. Look for cuts, staples through the wire, or loose connections at junction boxes and at the IVT control terminals.
• Test sensor: Disconnect the sensor and measure resistance. Compare to the IVT temperature/resistance table. Replace with the correct IVT outdoor sensor if readings are incorrect.

After replacement, verify that the displayed outdoor temperature on the control matches actual conditions within a few degrees.