A car's AC not blowing cold air can be caused by several common issues including:

• Low or leaking refrigerant: The refrigerant is crucial for cooling, and leaks lower its level, reducing cooling capacity.
• Clogged cabin air filter: A dirty filter restricts airflow, weakening the cool air output.
• Faulty compressor: The compressor pumps refrigerant through the system; if faulty, cooling fails.
• Damaged or blocked condenser: This component cools the refrigerant gas into liquid; blockage or damage lowers effectiveness.
• Electrical issues: Problems with wiring, sensors, or fuses can disrupt AC operation.
• Faulty blend door actuator: This part regulates whether hot or cold air enters the cabin.
• Pressure switch problems: These can cause the compressor to shut off if refrigerant pressure is abnormal.

Other causes include dirty evaporator, blocked expansion valve, or system contamination. Most common and critical causes to check first are leaking refrigerant and clogged cabin filter, followed by compressor or condenser problems. Professional inspection and servicing may be needed to diagnose and fix these issues effectively.