Common signs of ice buildup in an HVAC system include reduced airflow, increased energy consumption, and unusual noises such as gurgling or bubbling sounds. In severe cases, ice buildup can cause the system to shut down or freeze completely. Other signs may include water leaks, corrosion, or rust around the evaporator coil or other system components. It’s essential to monitor the system’s performance and address any unusual behavior promptly to prevent further damage.