I responded to the customer’s concern regarding insufficient heating performance. After completing a comprehensive system diagnostic, I confirmed that the thermostat was properly configured and that the Emergency Heat function was enabled to operate during low outdoor temperatures. During inspection of the outdoor unit, I identified a refrigerant leak which has resulted in the system operating with a low refrigerant charge. Due to this condition, the unit has entered a low-pressure lockout. This is a factory-installed safety feature designed to prevent compressor damage when refrigerant levels fall below safe operating limits. I reviewed available repair options with the customer and recommended scheduling an installation supervisor to provide a quote for equipment replacement based on the age and condition of the system. The customer declined further action at this time.The system is currently running in auxiliary heat only and will not run in cool/heat mode until the issue has been