To fix a car AC, first check if the air is blowing but not cold. Inspect the refrigerant level—low levels mean it needs a recharge. Use an AC recharge kit, following instructions carefully. Check the AC compressor; if it's not engaging, the issue could be electrical or mechanical. Examine fuses and relays for faults. If there's a strange smell or weak airflow, the cabin air filter might be dirty. Lastly, inspect for leaks using a UV dye kit. If problems persist, consult a certified mechanic, as deeper issues may involve the compressor or evaporator system. Always prioritize safety.