The most common cause is a system that is low on refrigerant, or Freon, but that’s not the only cause. A system that is not moving enough air through the duct system can also freeze up. Low airflow could be caused by an under-sized duct system, a dirty filter, or even a dirty indoor evaporator coil (often called an A-Coil). A frozen system can also be caused by setting the thermostat too low at night. What’s too low? Every house is different, but we’ve seen units freeze up at night when they are set to 68 degrees.
Quick Tip: Change your filters regularly to avoid impacted coils that could freeze due to a restriction from the debris. Small particles and not enough air flow or a restriction can cause a coil to freeze.