Wire Size Conversion Table; Circuit Malfunctions - GMC G Service Manual

The automatic reset breaker opens when excess current
heats a bimetallic strip, causing the strip to bend and open
a set of contacts. Then the strip cools and closes the con­
tacts. So the circuit breaker opens and closes until the
excess current condition is corrected or the circuit is discon­
nected from the power supply.
The remote reset circuit breaker has a heating wire
wound around the bimetallic strip. When an excess current
happens, the strip heats, bends, and opens the contacts.
Then a small current flows through the heat wire, keeping
the strip hot and the contacts open. This type of breaker will
stay open until either the power supply is disconnected
from the circuit or the breaker is removed from the circuit.
Then the breaker can cool and reset.
CIRCUIT CONTROLLERS
Circuit controllers consist of switches or relays. Switches
are usually operated by a mechanical means such as a
hand or lever. Switches are usually at the beginning of a
circuit but can be used to control a ground path. For exam­
ple, the switch controlling the headlights is at the power end
of the circuit while the door switch controlling the domelight
completes the ground path.
Relays are remotely controlled switches. They are used
in high current circuits and in circuits controlled by sensors.
Relays are designed so that a small current circuit will be
able to control a large current circuit.
WIRING HARNESS AND WIRES
Every wire is a specific size with colored or striped insu­
lation that is indicated on the wiring diagrams. Insulation
colors help to trace circuits and to make proper connec­
tions. Abbreviations and symbols used for indicating wire
insulation colors and patterns are as follows:
BLK ........ ............ Black
BRN ........ .......... Brown
CHK........ ..........Check
C R ........... .......... Cross
GRN........ .......... Green
NAT.......... ........ Natural
SGL ........ .......... Single
ORN........ ........ Orange
GR ........... ............. Gray
Some wires are grouped and taped together or encased
in a split plastic casing. This grouping of wires is called a
harness. For some purposes, it is more practical to use a
single wire protected by a braided tubing called a loom.
Wiring harnesses are joined by using a multiple plug and
receptacle connector block, or a terminal post chassis junc­
tion block. In the instrument panel area, plastic insulated
blade-type connectors and screw-type terminals are used.
Each harness or wire must be held securely in place by
clips or other holding devices to prevent chafing of the
insulation.
WIRE SIZE
Wire size in a circuit is determined by the amount of
current,- the length of the circuit and the voltage drop
allowed. Wire size is specified using the metric gage. The
PPL ........ ........ Purple
T R ............ .......... Tracer
YEL ........ .......... Yellow
.............
/ / ........ Parallel
WHT ........ .......... White
BLU ........ ............ Blue
STR.......... .......... Stripe
PN K ........ ............ Pink
........... ...........
D K Dark
GMTB-0104-1L
CAB ELECTRICAL 8A-3
metric gage describes the wire size directly in cross section
area measured in square millimeters.

WIRE SIZE CONVERSION TABLE

Metric
Size
(mm)2
0.22
0.5
0.8
1.0
2.0
3.0
5.0
8.0
13.0
19.0
32.0
40.0
50.0
62.0

CIRCUIT MALFUNCTIONS

There are three electrical conditions that can cause a
nonworking circuit; an "Open Circuit," a "Short Circuit," and
a "Ground Circuit."
OPEN CIRCUIT (Figure 3)
An open circuit occurs whenever there is a break in the
circuit. The break can be corrosion at the connector, a wire
broken off in a device, or a wire that burned open from an
overload of current.
v v w ^
—
T
Figure 3 — Open Circuit
SHORT CIRCUIT (Figure 4)
A short circuit happens when the current bypasses part
of the normal circuit. This bypassing is usually caused by
wires touching, salt water in or on a device such as a switch
or a connector or solder melting and bridging conductors in
a device.
AWG
Size
24
20
.18
16
14
12
10
8
6
4
2
1
0
00
GMTB-0105-1L
@ = H i '
B-00723