Automotive Electrical and Electronic Systems Classroom Manual Fifth Edition Update by John F. Kershaw

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112 Chapter Six
Figure 6-44.
The GM accessory circuit is color coded by circuit number. (GM Service and Parts Operations)
starter cable to 20 for a license plate lamp. Note that
gauge-size numbers are the reverse of physical wire
sizes: a lower gauge number for heavy wires and a
higher one for light wires. Figure 6-47 shows a typical
circuit using 20-gauge wire.
Most vehicles built in recent years specify wire
sizes by their diameter in millimeters (mm). In
this case, a starter cable might be 32 mm while a
typical circuit might be 1 mm or 0.8 mm. The wire
size appears next to the color and on the opposite
side of the wire from the circuit number, as shown
in Figure 6-46. Note that the “mm” abbreviation
does not appear in the diagram. An advantage to
using the metric system is that wire size corresponds
directly to thickness.
DaimlerChrysler Corporation. Nissan, like other
manufacturers, often includes the symbols with
its components, connector identification, and
switch continuity positions (Figure 6-51). Switch
continuity diagrams are discussed later in this
chapter. For more information about component
symbols, see the “Copper Wiring Repair” section
in Chapter 6 of the Shop Manual.
Figure 6-52 is a basic diagram of a Toyota
Celica sunroof control relay, which controls the
sunroof motor operation. Figure 6-53 shows how
the circuit is activated to tilt the sunroof open. The
current travels to the motor through relay number
one and transistor one when the “up” side of the
tilt switch is pressed.
Component Symbols
It is time to add new symbols to the basic
component symbols list (Figure 6-48). Figures
6-49A and 6-49B show additional symbols for
many of the electrical devices on GM vehicles.
Figure 6-50 illustrates symbols used by
DIAGRAMS
The color codes, circuit numbers, and symbols
just illustrated are combined to create a variety of
electrical diagrams. Most people tend to refer to
any electrical diagram as a “wiring diagram,” but