Figure 17-27. Wiper Arm and Blade
placed on the vehicle's 6-volt electrical system. This
windshield wipers are used almost exclusively on heavy
problem was solved as 12-volt electrical systems
vehicles that are equipped with a compressed air supply
became standard. The electric wiper motor, through a
system to operate the wiper motor. Air-operated wiper
worm gear, drives a shaft that is connected to a crank.
motors directly produce the reciprocating motion that is
The circular motion of this crank is transformed into
required to operate the wiper arms. Because of this, they
reciprocating motion by the wiper transmission to
often are mounted In a position that allows a wiper arm
operate the wiper arms. In addition to the control switch
to be connected directly to them.
that is used to control the windshield wipers, a separate,
mech- anically operated park switch also is Incorporated
17-17. Wiper Arm and Blade (Fig. 17-27). The wiper
into the motor. The purpose of this switch is to provide
arm fits onto a splined shaft on the wiper transmission
power to the wiper motor long enough to return the wiper
and is spring loaded to press the blade against the
arms and blades to a retracted position whenever they
windshield. The blade is a flexible rubber squeeze-type
are switched off by the operator.
device. It is spring steel backed and is suspended from
the arm by a mechanism that is designed to maintain
17-16.Air-Operated Wipers. Air-operated
total contact with the windshield throughout the stroke.
Section IV. ACCESSORIES
receptacle is wired in parallel with the battery. It is used
17-18. Auxiliary Power Receptacle (Fig. 17-28). The
to facilitate charging of the batteries from an external
auxiliary power receptacle usually is installed at the right-
source or the connecting of additional electrical power
rear corner of the cab body, near the vehicle batteries.
from an external source to operate electrical components
The receptacle has two insulated prongs, each
on the vehicle. The receptacle greatly simplifies these
connected by cable to one battery terminal. This means