Windshield wipers
See Figure 1

The first windshield wipers were an inside, hand-operated crank connected to an outside arm holding a rubber wiper blade, and operated back and forth by the driver. Later, for the convenience of the passenger, a blade and arm was installed on the passenger's side of the windshield and connected to the arm on the driver's side by linkage and operated in tandem with the driver's wiper.

This was unsatisfactory and was replaced by the vacuum wiper motor that operated the wiper arms using the vacuum from the car engine. This type of motor was used as late as the early '20s, mounted along the roof line and later moved to the cowl panel, directly below the windshield.

The major difficulty plaguing the vacuum motor was its inability to maintain a constant wiper blade speed. As the engine vacuum was lowered (when the car went uphill for instance), the wipers would stop and cause visibility problems. Vacuum holding tanks with one-way check valves and mechanical vacuum pumps were used to maintain a constant vacuum supply, but as the car designs changed, the windshield became larger and the wiper motor's work load increased. The added workload could not be handled by vacuum wipers.

Vacuum wipers gave way to electric wiper motors, first installed on cars as an option as early as 1940. The electric motor was dependable and could operate the wipers independent of the fluctuation in engine vacuum, and by 1972; all original equipment vacuum wiper motor installations had ceased.

Electric wiper motors are generally multiple speed units, with delayed or intermittent units used as options. A delayed or intermittent wiper control is used in a mist or light drizzle when the wipers are not continually needed. An adjustable time interval of three to twenty seconds is usually provided for the delayed wiper operation. Depending upon the manufacturer, the car may be equipped with multiple or adjustable intermittent settings that allow the driver to better control the wiper delay interval as necessary for the weather conditions.

Some import cars use delay wipers which are timed using an electronic control unit. The unit will vary the delay based on car speed, slowing or almost stopping the wipers while you are sitting at a light.

The electric wiper motor is a permanent magnet, rotary electric motor. A worm gear machined on the armature shaft drives the output shaft and gear through an idler gear and shaft. The output shaft operates the output arm, which is connected to the wiper linkage. As the electric motor revolves the output arm, the linkage is forced to move in a back and forth motion.

The speed of the electric motor is controlled by resistors, located on or in the control switch, and connected to the wiper motor electrical windings. The control switch directs the current through certain circuits of the wiper motor, as the driver desires.

Regardless of the type of drive motor used, the wiper linkage remains the same.

As the drive output arm is revolved or moved back and forth by the operation of the wiper motor, the force of this movement is transmitted by the linkage, to the linkage pivots, to which the wiper arms and blades are attached. As the linkage pivots are forced to rotate, the arms and blades move on the windshield in a predetermined arc.

Two types of linkages are used-depressed and non-depressed. The depressed types are hidden below the hood line when in the park position, while the non-depressed types are visible above the hood line when in their park position.

Windshield washers are installed in different cars in different ways.

All late model cars have the washers operated by electric motors, mounted separately or mounted in combination with the wiper motor. All types are controlled by the driver.

The nozzle arrangements are different in the respect that the locations can range from a single base with adjustable offset nozzles, to a single nozzle for the right and left sides, mounted on the cowl panel and individually aimed at the windshield.

Another location of the washer nozzles are on the wiper arms, distributing the fluid spray over the windshield as the arms go through their cleaning arcs.

On certain models, the washer pump can be activated and the wipers will automatically start and stop after a pre determined time, while on others the wipers must be stopped manually.

Plastic or rubber tubing is used to route the washer fluid from the reservoir, through the pump and check-valves, and to the washer nozzles.

Continue to Page 2 of Windshield Wipers and Washers

Back to top of page

Return to iCARumba Car Care Encyclopedia index