Page 323 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

3
Electrical systems 305

Indicators and hazard lights are interesting circuits. Hazard lights are intended
to show a hazard such as a broken-down car. They also seem to be used to
prevent parking tickets when in a restricted area; my experience is that this does
not work!

3.4 Body electrical and electronic systems

3.4.1 Washers and wipers

The requirements of the wiper system are simple. The windscreen must be clean
enough to provide suitable visibility at all times. To do this, it must:
achieve effi cient removal of water and snow
●
achieve effi cient removal of dirt
●
operate at temperatures from 30 to 80°C
●
pass the stall and snow load test
●
have a service life in the region of 1.5 million wipe cycles
●
be resistant to corrosion from acid, alkali and ozone.
●
Wiper blades are made of a rubber compound ( Fig. 3.101 ) and are held on
Key fact
to the screen by a spring in the wiper arm. The aerodynamic property of the
wiper blades has become increasingly important. The strip on top of the rubber The aerodynamic property of
element is often perforated to reduce air drag. A good quality blade will have the wiper blades has become
increasingly important.
a contact width of about 0.1 mm. The lip wipes the surface of the screen at an
angle of about 45°. The pressure of the blade on the screen is also important.
Most wiper linkages consist of a series or parallel mechanism ( Fig. 3.102 ).
Some older types use a fl exible rack and wheel boxes similar to the operating
mechanism of many sunroofs. One of the main considerations for the design of
a wiper linkage is the point at which the blades must reverse. This is because of
the high forces on the motor and linkage at this time. If the reverse point is set
so that the linkage is at its maximum force transmission angle, then the reverse

action of the blades puts less strain on the system. This also ensures smoother
operation.
All modern wiper motors are permanent magnet types. The drive is taken via a
worm gear to increase torque and reduce speed. Three brushes may be used,

Figure 3.101 Details of a wiper blade