Electric actuators are widely used on late-model vehicles to move the duct box doors. These actuators are used to move the blend door, the mode doors, and the fresh/recirculated air door. These actuators are typically mounted with very small fasteners in a location that allows them to be replaced without having to remove the whole duct box.
Many late-model cars, trucks, and sport utility vehicles (SUVs) have more complex HVAC systems that require less input from the occupants of the vehicle. With an increase in computing power, high-tech systems can now control the blower speed, air temperature, and air distribution point automatically by using electronic control heads or smart interfaces with touch screen capabilities along with many sensors and logic devices.
These automatic temperature control (ATC) systems operate in automatic mode by letting the operator set the desired temperature in the cab, and then the sensors, computers, and actuators operate to deliver the correct results. These systems most often have dual zone capabilities that allow the driver and the passenger to choose different temperature settings. The duct box is more complex with these dual zone systems because it is able to deliver air at different temperatures to each side of the vehicle. These systems also have some diagnostic capabilities built into the logic that will often display messages or codes when a problem is present in the system. The codes need to be researched in a technical database to determine the action needed to correct the problem.
ATC systems use modules, sensors, and actuators to control the temperature and humidity in the cab. The HVAC control module receives inputs from several sensors while communicating with the powertrain control module (PCM) over a data network. Both of these modules have control over the output devices that determine the temperature and humidity in the cab. The data link connector allows a scan tool to be connected to the vehicle to retrieve trouble codes and live data from the electronic systems on the
Vehicles with ATC are equipped with electronic control heads that allow the driver or the passenger to choose the desired temperature, and then the system automatically functions to achieve that temperature. Many of these ATC control heads also incorporate other functions into the platform, such as the audio system and the mobile phone
The duct box on vehicles with dual zone climate control is more complex because it can be configured to distribute cold air on one side and warm air on the other side of the vehicle. These duct boxes must have two air mix doors (temperature control doors) to accomplish this task. The doors on dual zone climate control systems are moved with electric
