Start with the simple checks
Make sure the AC button is on, the temperature is set to cold and recirculation is selected. Check that the blower works at every speed and that air comes out of the dashboard vents. If air flows but is not cold, the problem is in the refrigerant circuit; if little or no air comes out, it is usually the blower side.
Eight common causes
- Low refrigerant from a leak at a hose, joint, condenser or cooling coil – the most common cause. Topping up without fixing the leak only helps for a while.
- A failing compressor or compressor clutch, often with noise or a clutch that does not engage.
- A blocked or damaged condenser – dirt, insects or bent fins stop it releasing heat.
- A condenser fan that does not run, so cooling fades at idle and in traffic.
- A clogged cabin air filter that cuts airflow through the cooling coil.
- A failed blower motor or blower resistor – no air, or air only on the top speed.
- A faulty pressure switch or sensor that stops the compressor from running.
- A blocked expansion valve or a freezing cooling coil, which makes cooling come and go.
Cooling only fails in traffic
If the AC is cold on the highway but warm at signals, look at the condenser fan and the condenser first. At speed, air is forced through the condenser; at idle, only the fan moves air through it.
Getting the right part
Once a mechanic has found the faulty part, send the part name or a photo with your vehicle model, year and variant on WhatsApp. Rameswar Cool Spares supplies the parts for cars, SUVs, trucks and buses from its T. Nagar shop in Chennai and delivers across South India.