Service Manual User Manual

Electrical System
10-9
Model 3606 • Origin 10/99
10.4 WIRING HARNESSES
Wiring on the vehicle is contained within two separate
wiring harnesses, an engine harness and a cab harness.
There are several figures in this section that depict the
different wiring harnesses.
A harness consists of black-nylon woven braiding, provid-
ing a protective cover to bundle numerous wiring groups,
splices, terminals, connectors, and, where applicable,
diodes. Each harness is identified with a Trak part num-
ber when the vehicle leaves the factory.
One engine harness has been used throughout the pro-
duction history of this vehicle.
Note: There are currently three cab harnesses in use on
this vehicle. The initial harness covered serial numbers
8249 and before. The addition of wiring for limited acces-
sories on the next production harness covers serial num-
bers 8250 through 9398. The current harness covers
serial numbers 9399 and after and includes additional
wiring for all planned accessory items.
Check the cab wiring harness on the vehicle respective
of the serial number information above to determine
which harness the vehicle is equipped with.
Each wire is identified by a wire number on each end of
the individual wire, and by the color and gauge size of the
wire. The wire numbers and color codes are also identi-
fied on the appropriate electrical schematic. All circuits
have been electrically tested for continuity, and all diodes
have been tested for correct biasing. Where several indi-
vidual connectors appear, the wiring leading to a particu-
lar connector can help identify the specific circuit. For
some circuits, a colored band (tie wrap) is present,
affixed to the connector wiring and used as a color-code
indicator. For ease of identification, detailed illustrations
of each type of connector also appear in this section.
If wiring ever needs to be replaced, use the correct
gauge size wiring. NEVER replace a wire with a smaller
gauge wire.
a. Removal and Replacement
Remove a wiring harness only if damaged or unusable.
Install a new harness one terminal at a time as the old
harness is removed. Label or tag the terminal locations of
all wires, harness clips, tie wraps and conduit as the old
harness is removed to allow correct installation of the
new harness.
b. Disassembly
Disassembly of the wiring harness is not recommended
due to the precise arrangement of wires and splice
requirements. If it becomes necessary to replace wires,
use the correct gauge size wiring, and NEVER replace a
wire with a smaller gauge wire.
c. Cleaning and Drying
Clean a wire harness with a natural bristle brush and the
same detergent used to clean the vehicle. Allow the har-
ness to air dry. DO NOT allow surface temperatures to
exceed 300° F (149° C).
d. Inspection and Repair
Replace a harness only if it is damaged or unusable. If a
splice or repair must be made to a wire, always use rosin
core solder to bond wires together. Use heat-shrink tub-
ing or insulating electrical tape to cover all splices or bare
wires.
e. Installation
The wiring harnesses are held securely in place by wire
tie wraps, clips or other devices to help prevent chafing or
wearing of the insulation and entanglement with moving
parts. Sections of ribbed plastic conduit have been
installed where wiring or harnesses pass through open-
ings in the vehicle frame. Always install tie wraps, clips,
conduit, etc., in their original locations to help prevent
damage to the wiring or harnesses.
f. Wire Code and Color
The chart below indicates the wire code abbreviation and
color as used on the electrical schematics.
WIRE CODE COLOR
BLK Black
BLU Blue
BRN Brown
DK BLU Dark Blue
DK GRN Dark Green
GRN Green
GRY Grey
LGT BLU Light Blue
LGT GRN Light Green
ORN Orange
PNK Pink
PUR Purple
RED Red
TA N Ta n
YEL Yellow
WHT White