When your car's air conditioner is not cooling anymore — or worse, blowing hot air — it can make for an uncomfortable ride on a warm day. The solution could be a simple one, but it could also require a complex repair that would be risky to attempt at home.
While there are a variety of reasons your car's air conditioning might not be operating at top performance, the most common are a refrigerant leak, an electrical climate control issue, or a problem with the air conditioning compressor. Each of these can cause the AC to blow lukewarm or hot instead of cold air.
Your car's air conditioning uses refrigerant, a fluid designed to vaporize at a low temperature, to cool the air before it blows through the vents into the passenger compartment of the vehicle. If that refrigerant is leaking from somewhere in the AC system, it will become less effective at cooling the air before it leaves the vents.
A leak like this can be the result of a faulty component within the system, such as the compressor, evaporator, or hoses. Or it can just be a sign of age for an older vehicle, since the parts and hoses use rubber seals that naturally tend to wear over time, causing the refrigerant to leak.
Accidents and other damage can also cause refrigerant leaks. Since the AC condenser is in front of the radiator, it is susceptible to damage from flying road debris and other small front-end impacts. Another possibility is that AC hoses and pipes can rub against other parts while you drive, eventually causing a leak.
The buttons, knobs, and control screens that you use to adjust the temperature in your vehicle tell an AC/heater control module — basically a computer — to pass instructions to the heating and cooling system. Just like with any electrical tool or appliance, this component or the parts that support it, such as electrical wiring, can break down or fail for a variety of reasons. As a result, your car's AC could start to perform inconsistently, or even stop working altogether.
Due to the complex nature of the Air Conditioning System, an experienced and trained technician will need to evaluate the components to diagnose the true root cause, and ultimately repair or replace the faulty parts. You can help by clearly communicating and demonstrating the symptoms with the shop before they start working to fix this issue.