Start by doing a complete cleaning, disassemble everything and wash the condenser and evaporator with a pressure washer. Also the evaporator turbine xq when it accumulates earth does not throw away the air it owes. After that try it, if it stays the same it controls the refrigerant. If it is missing, it must be leaking, repair it and recharge the refrigerant. Before cleaning it, check if it is dirty with oil somewhere, if so, it is because it has a refrigerant leak in that area.