Furnace indicates thermostat/room sensor error; heating does not respond correctly to room temperature

Safety: Turn off power before working on thermostat wiring.

• Verify thermostat type: Ensure the installed thermostat or room unit is compatible with the IVT furnace (voltage, communication protocol, and contact type).
• Check wiring connections: Remove the thermostat cover and confirm wires are connected to the correct terminals as per the IVT wiring diagram. Tighten any loose screws.
• Inspect room sensor: If a separate IVT room sensor is used, check its location (not in direct sunlight or near heat sources) and wiring back to the control.
• Bypass test (for simple on/off): With power off, temporarily bridge the thermostat terminals at the furnace to simulate a heat call. Restore power; if the furnace runs normally, the thermostat or its wiring is suspect.

Replace faulty thermostats or sensors with IVT-approved components to ensure proper operation.