The answer to 'replacement freezing up' is that a frozen HVAC unit is a common problem that can have several causes, including a dirty air filter, low refrigerant levels, or a problem with the thermostat. Symptoms of a frozen unit include ice buildup on the coils, reduced airflow, and poor cooling performance. To fix a frozen HVAC unit, you may need to clean or replace the air filter, check the refrigerant levels, or troubleshoot the thermostat. In some cases, you may need to call a professional HVAC technician to diagnose and repair the issue.
It's generally best to call a professional HVAC technician if you're not comfortable troubleshooting and repairing the issue yourself. Attempting to fix a frozen HVAC unit without proper training and equipment can be dangerous and may cause further damage to the system.