Volvo VNL Service Manual page 21

Group 30 Electrical System—VNL, VNM
Ignition and Cranking Supply
•
From fuse 16, wire 243 supplies constant battery
power to the ignition switch.
•
When the ignition switch is turned to the IGNITION
position, power is supplied to wire 196, which ener-
gizes the Ignition Power Relay. From this relay, wire
196 supplies power to the bus bar for the Ignition
Maxi-fuses.
•
Two of the Ignition Maxi-fuses supply power to the
bus bars for the Ignition fuse positions: One Ignition
Maxi-fuse feeds wire 196–A to the bus bar for fuse
positions 5–12. The other Ignition Maxi-fuse feeds
wire 196–B to the bus bar for fuse positions 13–16.
•
When the ignition switch is turned to the START posi-
tion, wire 284 provides power from the ignition switch
to energize the starter relay coil. This completes the
circuit from the battery to the starter solenoid stud.
The solenoid is grounded directly to the starter.
System Ground
•
The engine ground is the common ground location
on the vehicle. The main cab ground stud 1 and the
frame rail ground meet at the engine ground stud.
Current is then carried through a fusible link to the
starter motor. This fusible link is designed to isolate
the positive and negative sides of the battery from
each other in the event of a positive battery cable
short circuit to the frame rail, cab, or engine. The
alternator is grounded by the 0A wire to the engine
block.
•
Ground stud 1 provides the main ground path to the
engine ground for the other cab ground studs. It is
installed at the same location as ground stud 7 (see
Starting and Charging System Logic Diagram ).
Design and Function
19