The answer to 'how to fix HVAC system' is to first identify the specific issue with your HVAC system. This may require troubleshooting common problems like a clogged air filter, low refrigerant levels, or a malfunctioning thermostat. Once you've identified the problem, you can often perform basic maintenance and repairs yourself, such as replacing the air filter, cleaning the condenser coils, or resetting the thermostat.
However, for more complex issues or if you're unsure of the problem, it's best to call in a professional HVAC technician. They have the expertise and equipment to properly diagnose and repair your HVAC system, ensuring it runs efficiently and safely. Regular maintenance by a professional is also recommended to prevent future breakdowns and extend the life of your HVAC system.