Freightliner FLA/FLB/FLC/FLD/FLL. Manual — part 39
Title of Maintenance Operation (MOP)
MOP Number
Electrical System Checking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54–01
Speedometer/Tachometer Cable Lubricating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54–02
Electrical, Instruments, and Controls
54
Index, Alphabetical
Heavy-Duty Trucks Maintenance Manual, April 1998
54–01 Electrical System
Checking
NOTE: Tighten electrical system connections to
the torque values in
Torque Values for Electrical System Connections
Connection
Torque:
lbf·in (N·cm)
Electrical Panel Stopnut
30 (340)
Air/Oil Junction Block Ring-Terminal Nut
30 (340)
Battery Terminal
70 (800)
Main Cab-Power Stud Hexnut
175 (1980)
Main Cab-Ground Stud Hexnut
50 (560)
Table 1, Torque Values for Electrical System
Connections
Cab Interior
Inspect the wiring and electrical connections at the
electrical mounting plate, cab-to-chassis interface
connectors, cab-to-engine interface connectors, main
cab-power and cab-ground studs, and electrical junc-
tion blocks.
•
For an FLA, see
and
•
For an FLB, see
and
•
For an FLC (LH DR), see
and
•
For an FLD, see
•
For an FLC (RH DR), see
and
For an FLA,
uncover the electrical mounting plate by
removing the tunnel top cover. The cover is held in
place by Velcro
®
. Pull upward on the left front and
rear corners, then tip the cover up and to the right.
Uncover the electrical junction block by removing the
tunnel right-hand kick panel.
For an FLB,
uncover the electrical mounting plate by
removing the tunnel left-hand cover. See
Ref. 3. Loosen the quarter-turn fastener (Ref. 2) at
the lower rear edge of the cover, then pull back on
the cover to unfasten the Velcro.
Remove the tunnel right-hand cover (Ref. 7) by mov-
ing the passenger seat up and back, removing the
screw (Ref. 4) at the upper left edge, and removing
the two screws (Ref. 6) at the lower right edge. Pull
the cover right and back, to clear the combo cover
and manifest box (Refs. 8 and 10). Then pull the
cover upward between the seat and tunnel.
For an FLC (LH DR),
uncover the main cab connec-
tors and studs by removing the right-hand under-
dash cover. See
, Ref. 1. Uncover the electri-
cal mounting plate by opening the glove box (Ref. 2),
then moving the stops at the upper edge of the box
toward each other, while swinging the glove box
down and out of the dash.
f540592a
10/20/93
Fig. 1, FLA Electrical Mounting Plate
f540040a
05/28/93
Fig. 2, FLA Electrical Junction Block
Electrical, Instruments, and Controls
54
Heavy-Duty Trucks Maintenance Manual, April 1998
54/1
For an FLD,
uncover the electrical mounting plate by
removing the access panel from the dash skirt under
the center section of the dash. The panel is attached
to the skirt by three quarter-turn fasteners.
For an FLC (RH DR),
uncover the main cab connec-
tors and studs by removing the left-hand under-dash
cover. See
. Uncover the electrical panel by
removing the glove box on the left side of the dash.
To remove the glove box, open the glove box door
and remove the six screws from the glove box liner.
See
. Then, remove the glove box door and
the glove box liner from the dash. This will expose
the electrical panel. See
Check all wiring for chafing, kinks, and discolored
insulation. Find the cause of any problems, then re-
pair, replace, or reroute wires as needed.
Check that all relays are firmly seated in their mount-
ing plates.
Check the tightness of the connections on the electri-
cal junction block(s), main cab-power stud, and cab-
ground stud, as equipped. Tighten the fasteners to
the torque values in
Install all of the removed panels.
Cab Exterior
For an FLC,
check the 40-way connector on the fire-
wall (left side for a RH DR vehicle and right side for
a LH DR vehicle), and check the power and ground
studs. Check the terminals for tightness, damage,
corrosion, and dirt. See
(LH DR) or
(RH DR).
Chassis
1.
Check the main chassis wiring harness. Check
the wiring insulation for damage from chafing or
08/24/93
f540610a
1
2
3
4
6
5
1.
Air/Oil Junction Block
2.
Electrical Mounting
Plate
3.
Circuit Breaker Bus
Bar
4.
Four-Position Junction
Block
5.
Two-Position Junction
Block
6.
Relays
Fig. 3, FLB Electrical Mounting Plate
f540630
1
2
3
4
5
6
2
8
9
10
11
7
14
13
12
10/20/93
1.
Bunk Harness Connectors
2.
Cable Tie Plate
3.
Main Cab-Ground Stud (Black)
4.
Seven-Way Receptacle Harness Connector
5.
Right-Hand Tunnel Side
6.
Electrical Mounting Plate (end view)
7.
Dash Support Bracket (end view)
8.
Daytime Running Lights Module
9.
Cab-to-Chassis and Cab-to-Engine Harness
Interface Connectors
10. Bulkhead Support Bracket
11. Main Cab-Power Stud (Red)
12. Main Cab Harness
13. Main Engine Harness
14. Right-Hand Cab Deck
Fig. 4, FLB Main Cab Harness Connectors
Electrical, Instruments, and Controls
54
Heavy-Duty Trucks Maintenance Manual, April 1998
54/2
heat. Also check for kinks. Reroute, repair, or
replace wires as needed.
CAUTION
Do not use flat-strip aluminum tie straps for hold-
ing electrical wiring. The sharp edges on these tie
straps may cause breaks in the wire insulation,
allowing the aluminum tie strap to make contact
with the wire. This could cause a short circuit and
damage to the wiring.
2.
Check all tie straps for breakage and damage.
Replace any broken or cracked tie straps.
3.
Check the wires of all sensors on or near the
engine. Make sure no wires are closer than 6
inches (15 cm) to hot surfaces. If any are, and
can not be rerouted, make sure they are pro-
tected by heat shields. Check that sensor con-
nectors are tight, clean, and undamaged.
4.
On engines with electronic controls, check the
wiring and connectors on the computer units.
LH HDLP
RH HDLP
HTR CONT
COMP CLT
SHTR
SHTDN
HTR HI
FAN Q
VH
FUEL
STG AID
INSTR
CLOCK
HORN
TR BLK
PNL LP
TRLR BLK
3A
1A
1B
1C
ACC
ACC
2A
2B
2C
3C
3B
PNL
LPS
GND
4A
4B
4C
X
PNL LP
MKR LP
RH HDLP
A/C
HTR
HT/AC
15
15
15
15
10
10
10
10
10
10
5
5
5
5
5
15
15
15
5
30
30
30
20
20
20
TRLR BRN
MKR LP
RD LP
LH HDLP
CIG LT
TR BRN
DIR SIG
SI LP
AIR DRY
ACCESS
RADIO
MID MIR
WIPER
LOAD
f540607
07/20/95
Fig. 5, FLC (LH DR) Electrical Mounting Plate
08/24/93
f540629
1
2
3
4
5
1.
Bottom of Dash
2.
Main Cab-Power Stud (Red)
3.
Main Cab Harness Interface Connector
4.
Main Cab-Ground Stud
5.
Right-Hand Side of Firewall (Inside Cab)
Fig. 6, FLC (LH DR) Main Cab Harness Connectors
f540276a
5
4
3
2
1
1
10/20/93
NOTE: Before March 15, 1990, the main cab harness
interface connectors were located on the firewall.
1.
Junction Block
2.
Main Cab-Power Studs (circuit 14 studs on junction
block)
3.
Relays
4.
Circuit Breaker Bus Bar
5.
Cab-to-Chassis and Cab-to-Engine Harness
Interface Connectors
Fig. 7, FLD Electrical Mounting Plate
Electrical, Instruments, and Controls
54
Heavy-Duty Trucks Maintenance Manual, April 1998
54/3
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