Chevrolet 1977 light duty truck, Руководство по обслуживанию

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Fig . 8 5 3 F u s e a n d C i r c u it B r e a k e r
instead o f a circuit breaker is the fuse in a one-tim e
protection an d replacem ent is required.
FUSIBLE L IN K (FIG . 8 -5 4 )
In addition to circuit breakers and fuses, the wiring
harness incorporates fusible links to protect the wiring.
Links are used rather than a fuse in w iring circuits that
are not norm ally fused, such as the ignition circuit.
w iring fusible links are color coded red in the
ch arg in g and load circuits to m atch color coding o f the
circuit they protect. Each link is four gauge sizes smaller
than the cable it is designed to protect and are m arked
on the insulation with wire gauge size because the heavy
insulation m akes the link a p p e a r a heavier gauge th an it
actually is.
E ngine co m p a rtm e n t w iring harnesses incorporate
several fusible links. The same size wire with special
hypalon insulation must be used w hen replacing a
fusible link.
T he links are:
1. A molded splice at the starter solenoid “ Bat”
term inal, 14 gauge red wire. Servicing requires splicing
in a new link.
2. A 16 gauge red fusible link is located at junction
block to protect all unfused w iring o f 12 gauge or larger.
The link is molded into the b ulkhead connector.
3. The g e n e ra to r w a rn in g light and field circuitry
(16 gauge wire) is protected by a fusible link (20 gauge
F ig . 8 -5 4--Fusible L in k
red wire) used in the “ battery feed to voltage regulator
# 3 te rm in a l” . The link is installed as a molded splice in
the circuit at the ju n ctio n block. Service by splicing in a
new 20 gauge wire.
D IA G N O S IS
Failures in a circuit are usually caused by short or
open circuits. O pen circuits are usually caused by breaks
in the wiring, faulty connections or mechanical failure in
a com ponent such as a switch or curcuit breaker. Short
circuits are usually caused by wires from different
components o f the circuit contacting one anothe or by a
wire or com ponent g ro u n d in g to the metal o f the body
due to a screw driven through the wires, insulation cut
through by a sharp metal edge, etc.
The following in fo rm atio n m ay aid in locating and
correcting a fuilure in the body wiring electrical system.
1. If a m ajor portion o f the electrical circuit
becomes inoperative simultaneously, the failure may be
due to im p ro p er connections between the front and rear
harness, or between the front harness and the chassis
wiring connector on top o f fuse block.
2. If only one o f the circuits is inoperative, the
failure is due to and open circuit or short in the affected
circuit. Short circuits usually result in blown fuses or in
the case o f power equipm ent circuits, in the circuit
breaker opening the circuit. If the fuse is not blown and
the circuit affected is a lam p circuit, check the bulb
before proceeding with any checking procedures.
3. The dom e lam p and courtesy lamp circuits are
designed so that the switches are in the " g r o u n d " side o f
the circuit. If a condition is encountered where the lamps
rem ain " o n " even though the j a m b or courtesy lamp
switches are not actuated, the failure is pro b ab ly due to
defective switches, or to the wire leading to the switches
being grounded to the metal body.
F U SIB L E L IN K BEFORE SHORT C IR C U I T
CUT WIRE HERE
FU S IB L E LIN K AFTER SHORT C IR C U I T