The electrical systems that are needed to allow the AC system to operate smoothly are very important. Using a logical approach will go a long way when trying to diagnose electrical problems in the AC system. It is a wise strategy to test all of the functions of the HVAC system to see what works and what does not work. For example, if there is no operation from any of the HVAC systems, then the problem is likely to be a main power problem, such as a fuse or a main ground.
Vacuum actuators can be used as a method to move the duct doors on older cars and trucks. These devices are typically connected to a duct door with some type of linkage and will be operated by sending vacuum through a hose to cause movement. These actuators are spring loaded to a fixed position and the vacuum causes them to create linear movement, which causes the duct door to
Electric actuators are commonly found on cars and truck duct boxes. These small bidirectional motors are connected to the duct doors and cause movement of the door when voltage is sent to the motor from the HVAC control module. These actuators sometimes need to be recalibrated if battery power is lost on the vehicle. This calibration can be commanded with a scan tool or by pressing a sequence of buttons on the HVAC control
