How do you fix low refrigerant?

Fixing low refrigerant in a residential or automotive air conditioning system requires a comprehensive repair process rather than simply adding more gas, because cooling loops are sealed systems where low levels always indicate a leak. First, turn off the air conditioning system immediately to protect the compressor from overheating. Second, contact a certified HVAC technician or automotive mechanic to perform professional pressure testing, electronic sniffing, or UV dye injection to locate the exact source of the leak, such as a cracked coil, a damaged hose, or a failed O-ring. Third, have the leaking component repaired or replaced. Fourth, evacuate all remaining air and moisture from the closed loop using a vacuum pump before recharging the system with the exact factory-specified weight and type of refrigerant. You can verify success when cold air returns.