The air conditioning (AC) in a car is controlled by a system that includes several key components:

1. Climate Control Unit: This is typically located on the dashboard and allows you to adjust the temperature, fan speed, and air distribution. Modern cars often have digital climate control systems that let you set specific temperatures.
2. AC Compressor: This component compresses the refrigerant and circulates it through the AC system. It’s controlled by the engine and usually engages when you turn on the AC.
3. Condenser: This component helps to cool the refrigerant after it’s been compressed by the AC compressor.
4. Evaporator: This component cools the air that blows into the cabin by transferring heat from the air to the refrigerant.
5. Expansion Valve or Orifice Tube: This regulates the flow of refrigerant into the evaporator.
6. Blower Motor: This controls the airflow through the vents. You can adjust the fan speed to control how much air is blown into the cabin.
7. Temperature Sensors: Modern cars use sensors to monitor the temperature inside and outside the car to maintain a consistent climate.

When you adjust the settings on your climate control unit, it sends signals to these components to adjust the temperature, airflow, and distribution of the air to achieve your desired comfort level.

The part that directly controls the AC system in a car is the climate control unit or AC control module. This component is typically located on the dashboard and allows you to adjust the temperature, fan speed, and air distribution settings.

In modern cars, the climate control unit might be integrated with a digital display and electronic controls, while in older models, it might be a more traditional set of dials and buttons. This unit sends signals to other components of the AC system, like the AC compressor, blower motor, and blend doors, to adjust the cabin temperature and airflow according to your settings.