The most common reason your car's AC isn't working is a refrigerant leak. The system is sealed, and if refrigerant escapes, there's nothing left to cool the air. However, other frequent culprits include a faulty blower motor (no air from vents), a failed compressor clutch (the main AC component doesn't engage), electrical issues like a blown fuse, or a blockage in the system.
Before you assume the worst, check the simple things first. Is the AC button actually lit up? Is the fan speed set high enough? Sometimes, the issue is just a control panel glitch.
If the basics check out, the problem is likely mechanical. A functioning AC system relies on a cycle where refrigerant changes from a liquid to a gas, absorbing heat from the cabin. The compressor is the heart of this system. If you turn on the AC and hear a click but the engine doesn't briefly bog down, the compressor clutch may not be engaging, often due to a lack of refrigerant or an electrical fault.
Here's a quick guide to symptoms and their likely causes:
| Symptom | Most Likely Cause | Other Possible Causes | Typical Repair Cost Range (USD) |
|---|
| AC blows warm air | Refrigerant Leak | Compressor Failure, Clutch Issue | $200 - $1,500+ |
| AC blows cold air only sometimes | failing Compressor Clutch | Electrical Issue, Refrigerant Level Low | $300 - $1,000 |
| No air comes from vents | Blown Fuse, Blower Motor Failure | Resistor Issue, Wiring Fault | $50 - $800 |
| AC blows cool, not cold | Low Refrigerant, Clogged Cabin Air Filter | Condenser Issue (blocked) | $100 - $400 |
| Unusual noises when AC is on | Worn Compressor Bearings, Debris in Fan | Failing Blower Motor | $400 - $1,200 |
| Foul smell from vents | Mold/Mildew in Evaporator Core | Dirty Cabin Air Filter | $100 - $300 (cleaning) |
What you should do: For refrigerant-related issues, a professional must handle the repair. They will use a machine to safely recover any remaining refrigerant, fix the leak, and then recharge the system to the manufacturer's specification. Attempting a DIY fix with store-bought recharge kits can damage the compressor if overfilled and is illegal in some states if not performed by a certified technician. For blower motor or fuse issues, a trusted mechanic can usually diagnose and fix the problem quickly.
