Page 337 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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Electrical systems 319

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Figure 3.123 Circuit for electric windows

Figure 3.124 Electric window lift motor

( Fig. 3.125 ). When a current is passed through the elements, heat is generated
and the window will defrost or demist.
This circuit can draw high current, 10–15 A being typical. Because of this, the
circuit often contains a timer relay to prevent the heater being left on too long
( Fig. 3.126 ). The timer will switch off after 10–15 minutes. The rear screen
elements are usually shaped to defrost the area of the rear wiper blade resting
position, if fi tted.
Front windscreen heating is used on some vehicles ( Fig. 3.127 ). This presents
more problems than with the rear screen, as vision must not be obscured. The
technology used is drawn from the aircraft industry and involves very thin wires
cast into the glass. As with the heated rear window, this device can consume a
large current and uses a timer relay.