Wiper System Glossary & FAQs

Wiper System Glossary

Arm Length

The distance from the center of the pivot shaft to the center of the wiper blade.  Find out more about how to measure a wiper arm.

Breakaway Curve

The place where the curve of the glass becomes too great to wipe.

The connector at the end of the pantograph arm which attaches the idler to the driver and mounts the blade.


A washer fluid fitting that provides passage through the bulkhead. The washer hose from the pump connects to the inside of the fitting. The washer hose to the nozzles connects to the outside of the fitting.

Bulkhead Fitting

A motor that needs a power source to park the terminal. When the park circuit is energized, the motor continues to run until it reaches its assigned park position. There, the power is disconnected on the motor’s park-plate internally. The motor stops because the power is disconnected.

Coast to Park Motor (12V/24V)

A link with two bearings that connects the motor drive arm to the pivot shaft.

Connecting Link

The straight-line distance that the center of the blade travels in its sweep pattern measured in inches.


The area of the windshield glass that you can see through from the inside edges of the moulding.

Daylight Opening (DLO)

A crank arm that bolts onto the output shaft of the motor and drives the connecting linkage.

Drive Arm

A motor that is electrically locked in its park position. When the circuit is energized, the motor continues to run to its assigned park position. There, it stops very positively and will not move. This method of wiring is usually utilized where high winds or heavy snow carry the momentum of longer arms and blades past the normal coast to park circuitry.

Dynamic Park Motor (12V/24V)

The unswept area of the glass beyond the cord length.


A sweep pattern in which the blade stays parallel to the side of the glass.


A plate which supports the pivot post for the idler of a pantograph arm.

Pantograph Adapter

The pivot shaft transfers power from the wiper motor via an oscillating connecting link to the wiper arm.  The wiper arm is attached to the pivot shaft on the outside of the vehicle.

Pivot Shaft

An arced sweep pattern. The arms are sometimes called “standard arc” or “pendulum” type.


The amount a wiper arm moves in and out as it follows the curvature of the glass.

Rise (or Rise and Fall)

A channel at the end of the wiper arm where the center of the wiper blade attaches.


The arc of the wiper arm measured in degrees.

Sweep Angle

The amount of force exerted on the blade by the spring tension of the wiper arm.

Tip Force


Wiper System FAQs

A:  You might be surprised to learn that the actual length of a wiper arm is longer than its designated length. That’s because the industry standard approach is to designate wipe arm length as the straight line distance from the center of the pivot shaft to the center of connection to the wiper blade.  Read more and see an illustration in our post:  How to Measure Wiper Arm Length.

Q:  How should I measure wiper arm length?

  • A radial wipe pattern is best when your glass is wider than it is tall.
  • A pantograph pattern works better on tall, narrow glass.

Usually, the pivot locations are close to the window for radial patterns and farther away for pantograph patterns.

Q:  Which sweep pattern is best for my application?

Wiper motors are rated by stall torque. This is usually expressed in Newton meters (Nm).

  • A 38 Nm motor is recommended for arm and blade combinations of 28” (710 mm) and longer and for multiple arms and blades driven by one motor.
  • A 30 Nm motor is suitable for arms and blades in the 20” to 28” (500 mm to 710 mm) range.
  • A 12 Nm motor is appropriate for arms and blades in the 16” to 20” (400 mm to 500 mm) range.
  • An 8 Nm motor works well for small arm and blade combinations of 16” (400 mm) and under.

Often motors of 20 Nm or less have internal linkage to make the necessary oscillating motion.

Q:  Which wiper motor should I use?

  • Coast to Park Motors – When turned off,  the motor “coasts” to a mechanical stop.  The park position can vary by several degrees on coast-to-park motors.
  • Dynamic Park Motors –  When turned off, the motor electrically locks into the park position.  Park position is always consistent on dynamic park motors.

Q:  What's the difference between coast to park and dynamic park motors?

12 V DC motors draw about 5 amperes during normal use. Under heavy snow or wind loads, the draw will increase.

  • We recommend you use a 10 amp circuit breaker for one 12 V DC motor, or a 15 amp circuit breaker for a two motor system.
  • For 24 V DC motors, use a 5 amp breaker for one motor and a 7 amp breaker for two.

Q:  What circuit protection should I provide my wiper motor?

Yes you can, when you’re also using a one-speed coast to park motor.

If you need to, you can use a toggle switch on the low speed (only!) on a two-speed coast to park motor.

  • Wire the park circuit “hot” through the ignition switch directly.
  • Use a single-pole, single-throw switch to energize the low speed brush.

REMEMBER: Do not use toggle or rocker switch with the high speed on a two-speed motor!

Q:  Can I use a rocker or toggle switch with my self-parking wiper motor?

Looking at the windshield from outside of the vehicle, the wiper arm and blade must travel in a clockwise direction or counterclockwise direction to park, referenced as clockwise to park (CW) or counterclockwise to park (CCW).

Q:  What is parking position?

Over the years, the mainstream manufacturers have each developed their own standards for wiper arms.

  • Drum interfaces were popular in 1950s and 1960s automobiles.
  • The tapered knurl is commonly found on many off-road applications, as well as larger applications such as motorhomes and buses.
  • The European DIN standard is the latest world-wide adopted interface and can be found on all types of equipment.

Q:  Why do wiper arms and shafts have so many interfaces (i.e. knurl, drum, tapered knurl, DIN)?