The answer to 'air handler freezing up' is that a frozen air handler is a common issue that can be caused by a few different factors, including a clogged air filter, low refrigerant levels, or a problem with the blower fan. Symptoms include reduced airflow, the unit not blowing cold air, and ice buildup on the coils.
If you notice your air handler is freezing up, the first step is to check the air filter and replace it if it's dirty. You'll also want to ensure the airflow around the unit is not blocked. If the problem persists, it may be due to low refrigerant levels or an issue with the blower fan, which are best diagnosed and repaired by a professional HVAC technician.