More refrigerant in a system than it was designed for.
Extra refrigerant backs up as liquid in the condenser, raising subcooling and head pressure and cutting the condensing surface available. Superheat tends to be low, with a risk of floodback. The fix is to recover the excess, not to vent it. Confirm airflow and coil condition first, because a dirty condenser also raises head pressure.
Exam work areas
F · Maintenance, service and troubleshooting