The wiper motor switch operates with a wiper motor relay which functions to open or close the electrical circuit. The wiper motor relay basically acts as an ON/OFF voltage control switch, by closing or opening the contacts that provide voltage to the wiper motor, and works when the wipers are turned on.
The wiper motor relay will be housed in the relay box, usually found underneath the dashboard. The relay connects to the car's battery, as well as connecting to the specific part that the relay is functioning, in this case the wiper motor. The wiper motor relay uses an electromagnet to mechanically operate the wiper motor switch. The relay is made up of a coiled wire which is attached to a strong magnetic base, such as iron, which generates a magnetic field when the electric current flows through it, which activates the wiper motor switch and either opens or closes the connection. The relay has a hinged mechanism which enables the switch to move, which either starts or stops the current to the motor.
When the wiper motor switch is activated by the driver via the controls on the wiper stalk switch, the wiper motor relay allows an electric current to flow to the wiper motor. The copper winding in the wiper motor picks up this current causing the electricity to move through the wiring. The electricity moving through the cooper wire creates a circular magnetic field. It is this magnetic energy which generates the force to power the cylinder in the motor and makes it spin. The spinning cylinder creates the energy needed to power the motor which in turn powers the wiper mechanism. When the wipers have been set to the off position on the wiper stalk switch, the wiper motor switch, with the action of the wiper motor relay, is designed to interrupt the flow of current from the battery to the wiper motor. The wiper motor switch controls the levels or voltage of the current flowing to the motor, to enable the different speed settings which can be chosen by the driver. When a slow or medium speed setting is selected by the driver, when the motor has reached the necessary speed for the chosen setting, the wiper motor switch, with the mechanism of the motor relay, activates or deactivates according to the rotating speed of the motor. The windscreen wiper arms are programmed to automatically return to the park position when the wipers have been switched to off, which means they will not obstruct the driver's view when not in use. The controller for intermittent wiper mode is often built into the wiper motor switch and managed by the wiper motor relay.
Faults can occur with the electrical contacts, relay coil and wiring. The connections can overheat and corrode. Moisture can also seep inside the relay which can compromise the proper functioning of the wiper motor relay. It is important when replacing the wiper motor relay that you buy a part that will be compatible with the make and model of your vehicle. Buying the wiper motor relay will guarantee you get the right component that is designed specifically for the make and model of your car.