Actuators are commonly used in automobiles to operate different aspects of the vehicle. Headlights, air conditioning and cruise control are all different parts of a vehicle that use an actuator to operate. In older model vehicles, there are vacuum actuators that also control the doors. In different cars, there may be either an electrical actuator or a vacuum pull actuator. Electrical actuators rely on the electrical system to operate, while vacuum pull actuators rely on the engine vacuum system.
While a vacuum actuator acts in conjunction with both valves and throttles, the general function of the actuator remains the same. A vacuum actuator has a chamber that it uses to create vacuum pressure. As air leaves the actuator, a vacuum is created, which causes outside pressure to act on the diaphragm of the actuator. The pressure then overtakes the spring inside the actuator and allows it to open. This action sends pressure through the cables and to the throttle.
Within the engine, there is a canister or reservoir that creates a vacuum. Vacuum pressure used by the actuator is initiated within this reservoir. The actuator attaches to the vacuum system through a series of tubes run from the vacuum system to the actuator. The vacuum operates through a solenoid valve and engages or disengages the throttle. In newer model cars, the vacuum pull actuator is part of a system that helps control speed based on how close the vehicle is in proximity to the vehicle driving in front of it.
In a cruise control system, the cables attach to the vacuum actuator and the gas pedal. The computer that operates the cruise control has a vacuum valve control signal that sends a signal to the vacuum actuator. The actuator has a valve that attaches to a cable, which then attaches to the throttle valve. This valve controls the throttle, making it engage or disengage according to the vacuum pressure.