Page 336 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

3
318 Automobile mechanical and electrical systems

Supply
+
Other systems
+ lgn

ECU and relays

M M M M
Window motors and position sensors

Driver’s
switch
Door pack
switch Door
circuit switches
for each
window

Figure 3.122 Electric window system block diagram

By counting the number of pulses received, the ECU can also determine the
window position. This is important, as the window must not reverse when it
stalls in the closed position. In order for the ECU to know the window position, it
must be initialized. This is often done simply by operating the motor to drive the
window fi rst fully open, and then fully closed. If this is not done then the one-
touch feature and bounce-back will not operate.

A ‘lazy-lock’ feature allows the car to be fully secured by one operation of a
remote key. This is done by linking the door lock ECU and the window and
sunroof ECUs. A signal is supplied and causes all the windows to close in turn,

and then the sunroof, and fi nally locks the doors. The alarm will also be set if
required. The windows close in turn to prevent the excessive current demand
that would occur if they all tried to operate at the same time.
A circuit for electric windows is shown in Fig. 3.123 . Note the rear window
isolation switch. This is commonly fi tted to allow the driver to prevent rear
window operation, for child safety for example.
Most window lift motors ( Fig. 3.124 ) are permanent magnet types and drive
through a worm gear. This reduces speed and greatly increases the torque.
All of the systems examined in this section are based on motor reverse circuits.
Door locks, windows, sunroofs, mirrors and seats all operate in this way. Most of
the systems are designed to improve driver and passenger comfort.

3.4.6 Screen heating

Electrical heating is used for screens, windows, seats and mirrors. Some heavy
vehicles also incorporate cab heaters, which use fuel from the tank. As far back
as the 1920s, when vehicle heaters were not fi tted, electrically heated gloves
were available. Beware of short-circuits!
Heating of the rear screen involves a circuit with a relay and usually a timer.
The heating elements are thin metallic strips bonded to, or built inside, the glass