Call a professional for emergency furnace repair if you experience a complete system failure, no heat despite the thermostat being set appropriately, unusual noises like banging or grinding, a malfunctioning pilot light, or the presence of gas odors. Additionally, if your furnace repeatedly cycles on and off, exhibits signs of overheating, or if there are visible signs of damage, it's crucial to seek immediate professional assistance. Prompt attention to these issues ensures the safety, efficiency, and continued functionality of your heating system.