- Windshield wipers consist of a pair of arms with blades attached that pivot to push water away from a surface. Windshield wipers operate via an electric motor, although past versions received power through a vacuum motor, which in turn were powered by the manifold vacuum.
- A manifold vacuum, which draws its power from the internal combustion engine, refers to the partial vacuum provided at the intake manifold. The piston engine acts as an air pump by supplying the suction necessary to produce the manifold vacuum.
- The manifold vacuum relies on throttle position to produce a partial vacuum, which decreases almost to nearly a non-existent level when the throttle is wide open. This lack of vacuum causes the wipers to slow or stop. This issue was minimized in some vehicles through the installation of a fuel/vacuum booster pump.