The answer to 'system upgrade freezing up' is that a common cause is an issue with the refrigerant charge in the HVAC system. Symptoms may include the system icing up, blowing warm air, or shutting off unexpectedly. Solutions can include adjusting the refrigerant level, cleaning the coils, or addressing other underlying issues.
If the system is frequently freezing up, it's best to have a professional HVAC technician diagnose and repair the problem. Attempting DIY refrigerant charging or other complex repairs can be dangerous and may void the system's warranty. It's important to have a qualified technician inspect the system and make any necessary adjustments or repairs.