The answer to 'tune-up freezing up' is that there are several common causes for an HVAC system freezing up, including low refrigerant levels, blocked airflow, and issues with the thermostat or other components. Symptoms may include ice buildup on the coils, poor airflow, and the system cycling on and off frequently. Solutions can involve recharging the refrigerant, cleaning the coils and filters, or troubleshooting and replacing faulty parts.
In many cases, the cause of a freezing HVAC system can be diagnosed and repaired by a homeowner, but it's important to exercise caution when working with refrigerant or electrical components. For more complex issues or if you're not comfortable troubleshooting the problem yourself, it's best to call in a professional HVAC technician to properly diagnose and fix the issue.