Section 06: ELECTRICAL
PA1562
4
1. GENERAL DESCRIPTION
This vehicle uses a dual voltage system to
obtain two different voltages (12 and 24 volts)
for various electrical controls and accessories.
The main power source incorporates four
maintenance-free “Volvo” model 20359831
batteries connected in parallel-series. All
batteries are kept uniformly charged by means
of a 100 amp battery equalizer (standard), giving
a maximum possible output supply of 100 amps
on the 12 volt system. Both the 12 and 24 volt
systems are controlled through individual main
battery relays. Two 24 volt self-rectified
alternators are belt driven from the engine, and
can be reached through the engine
compartment doors.
1.1 WIRING DIAGRAMS
A master wiring diagram of the electric circuits,
covering standard and optional accessories and
systems, is located in the technical publications
box. Usually, a separate wiring diagram page is
provided for each major function or system. In
some cases, more than one circuit may appear
on one wiring diagram page; when this occurs,
each circuit covered in this page is listed in the
wiring diagram index. Moreover, a circuit may
appear on several pages; in such case, the
number(s) at the extremity of the diagram title
will indicate the sheet reference number. Refer
to the "Wiring Diagram Index" to ensure that the
correct diagram is being used to trace the circuit
in question. In addition to the major functions
page reference, the wiring diagram index
contains the following information pages.
o The Multiplexed Device Index,
o The Arrangement-Harness drawing showing
the harnesses arrangement and harness
number on the vehicle,
o Glossary,
o Circuit number listing,
o Circuit breaker code,
o Connector code,
o Diode number code,
o Resistor number code,
o Fuse code.
1.1.1 Using Wiring Diagrams
Three methods are used to "work" with electric
wiring diagrams.
Situation: You have identified the defective part
(breaker, diode, relay, etc.), and you wish to
locate its corresponding circuit.
Problem: Circuit breaker CB12 is released
(open circuit) and you don't know which circuit is
affected.
a) Refer to wiring diagram index, and look for
"Circuit breaker code", pages F.
b) At item CB12, you will find the location, the
Prevost number, the breaker function, the
breaker ampere rating and the page on
which to find the corresponding diagram.
c) Refer to page 3.1.
d) When you have located CB12, follow the
wiring up to the end and find the diagram
page number and function on which the
circuit continues.
Situation: You have a problem with a specific
system and you want to find the corresponding
diagram.
Problem: The last three (3) speakers on the
R.H. side of vehicle are inoperative and you
must trace the electric circuit.
d) Refer to wiring diagram index and look for
“Sound system”.
e) You will find on page 35.1 & 35.2 the
components as well as the electric wiring,
thus providing you with a complete
understanding of this circuit.
Situation: Using the message center display
(MCD), you check on arrival if there are active
errors in the vehicle electrical system. With the
SYSTEM DIAGNOSTIC menu, highlight FAULT
DIAGNOSTIC, highlight ELECTRICAL SYSTEM
to request a diagnostic of the electrical system
and then press the enter key. If applicable, the
MCD shows the fault messages or fault codes
recorded. When more than one fault is recorded,
an arrow pointing down appears on the right of
the display. Use the down to see all the fault
messages.
Problem: MCD displays the fault "Elec. Horn
SW61 SW62; shorted to ground" as being
active.
a) Refer to wiring diagram index, and look for
"Multiplexed Device Index", pages B1-B8.
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