The answer to 'zone control system freezing up' is that there are several common causes, including low refrigerant levels, airflow blockages, thermostat issues, and problems with the zone dampers or control board. Symptoms may include ice buildup on the coils, uneven heating/cooling, and the system short-cycling. Solutions can involve checking and adjusting refrigerant levels, clearing airflow obstructions, replacing faulty components, or recalibrating the thermostat.
In many cases, troubleshooting and resolving a frozen zone control system requires the expertise of a licensed HVAC technician. While some basic maintenance tasks like changing air filters can be done DIY, more complex issues with the refrigeration system or electronic controls are best left to the professionals to avoid further damage or safety hazards.