Furnaces play an important role in keeping homes warm during winter. Annual inspection and maintenance prevents major repairs and replacements down the line. Common furnace problems include malfunctioning thermostats, air flow issues caused by worn parts like bearings or belts, and dirty air filters that clog the system. It is best to call a professional to diagnose and fix any issues, as problems with switches, leaks, or continuously running blowers could be dangerous if not addressed properly.