Furnace indicates outside temperature sensor fault, weather-compensated control not working

Safety: Isolate power before working on control wiring.

• Locate outdoor sensor: Find the Hoval outdoor temperature sensor on an external wall, away from direct sun.
• Inspect housing: Check for cracks, water ingress, or insect nests. Dry and clean if necessary.
• Check cable: Follow the cable back indoors, looking for damage or junction boxes with loose terminals. Tighten all connections.
• Verify correct sensor: Ensure the installed sensor matches the Hoval specification for your controller.
• Reset controller: Restore power and clear the error. If the fault remains, replace the outdoor sensor.