The answer to 'why is my HVAC system not working' is that there are several common causes, including a clogged air filter, a malfunctioning thermostat, a refrigerant leak, or a problem with the compressor or blower motor. Symptoms may include the system not turning on, poor airflow, uneven heating or cooling, or high energy bills.
Some issues, like a clogged filter or a thermostat problem, can often be fixed through simple DIY troubleshooting and maintenance. However, more complex problems like refrigerant leaks or compressor failures usually require a professional HVAC technician to diagnose and repair. Attempting to work on these components yourself can be dangerous and may even void your warranty.