An automatic air-conditioner is a manual air-conditioner and heating system equipped with sensors which detect changes in ambient temperature, cabin temperature and solar radiation.
The electronic control unit evaluates the signals from the sensors to determine the operating conditions, and controls actuators to move dampers and valves that control the volume, temperature and direction of the air delivered by the system.
The climate control system can be operated in manual mode, where the operation is similar to a normal heater and air conditioner system. The driver determines where the air is delivered, the volume of air delivered and its temperature.
Or it can be operated in full automatic mode.
In full automatic mode the electronic control unit receives signals from sensors and controls the flaps and valves of the two systems, to create a blend of air that matches the temperature selected by the occupants.
The electronic control unit or ECU contains a micro-computer. It is constructed from printed circuitry and has a large number of electrical components and electronic devices. It is normally housed in a metal or plastic container. On some automatic climate control air-conditioning systems the control panel is part of the electronic control unit.
The electronic control unit receives signals in the form of voltages from the ambient air temperature sensor, the cabin air temperature sensor, the coolant temperature sensor, the evaporator temperature sensor, sun load sensor and the control panel.
The electronic control unit compares these voltage values with values stored in its memory. If a difference in values occurs the electronic control unit changes the position of actuators.
The actuators are electric solenoids and electric motors which control the position of doors and taps either directly, or by vacuum servos.
The electronic control unit also controls the speed of the interior ventilation fan. The speed of the fan is infinitely variable between a stopped condition and the fan's maximum speed.
Some actuators provide a feedback signal to the electronic control unit in the form of a voltage signal. This signal is used by the electronic control unit to determine what position the actuators are in, and whether or not they are moving.
