How car AC works, in plain words
Your AC moves heat out of the cabin. A gas called refrigerant does the work. The compressor is a pump that squeezes the refrigerant. The condenser in front of the radiator lets the heat out. The evaporator behind the dash soaks up heat from the cabin air.
When all of it works, cold air comes out. When one part fails, you get warm air. The trick is finding which part.
The top cause: low refrigerant from a leak
AC systems are sealed. They do not use up refrigerant. If it is low, it leaked out. Common leak spots are a hose, an O ring, the condenser or a seal in the compressor.
A small leak can take a year to show up. A big leak can empty the system in a week. We add a dye and use a leak detector to find the spot. Then we fix the leak and pull a vacuum on the system. We fill it to the exact weight your car calls for.
Other causes of warm air
If the refrigerant is full, we look at these next.
- A bad compressor. If the clutch will not engage, nothing moves.
- A blocked condenser. Bugs, leaves and road grime stop it from letting heat out.
- A cooling fan that quit. The AC gets warm at a stop but cool at speed.
- A stuck blend door. This is the flap in the dash that mixes hot and cold air. You may hear a click behind the dash.
- A clogged cabin air filter. Airflow gets weak and the air feels warm.
- An electrical fault. A relay, a pressure switch or a fuse can shut the system off.
Why a can from the store is a gamble
A recharge can from the store may cool the car for a while. But it does not fix the leak. The gas just leaks out again.
Many cans have a sealer in them. Sealer can clog the small passages in the system. Then the fix costs more than it should have. Too much refrigerant is also a problem. It can make the AC blow warm and hurt the compressor.
Newer imports use a different type of refrigerant than older cars. It needs its own equipment and the right training. Ask us about your car before you buy a can.
Georgia heat and your AC
Summers in Athens, GA run hot and humid for months. Cars parked at UGA or in a lot on Lexington Road bake all day. Your AC works harder here than in most places.
Heat also shows weak spots fast. A system that felt fine in April may blow warm in July. If your AC is only a little cool on a hot day, the system is likely low. Have it checked before the next heat wave.
What an AC check at our shop looks like
We check the pressure on both sides of the system. We watch the compressor and the fans. We check the vent temperature. We look for dye at the leak spots. Then we tell you what we found and what it needs.
Not sure what your car needs? Call Athens Import Auto Repair at 706-353-3880 and tell us what you feel. Warm air, weak air or a strange noise all help us narrow it down.
Key takeaways
- A refrigerant leak is the most common cause of warm AC.
- Warm at a stop but cool at speed points to the fan or condenser.
- A can from the store does not fix the leak and can clog the system.
- Georgia heat shows a weak AC fast.
- A pressure test and a leak check find the real cause.
