Power and Ground Distribution: Description and Operation

Power and Grounding Circuit Description

A single, dual or triple battery supplies electrical power to operate the vehicle's electrical system. At the positive battery attachment, the positive battery cable connector has two heavy gauge insulated electrical cables.

The first, larger gauge, battery cable is connected to the starter solenoid B stud with a large ring terminal, C1. The second, smaller gauge, battery cable is connected to the fuse block 1 and fuse block 2. with a ring terminal.

With starter solenoid terminal C1 connected, the starter solenoid B stud serves as a junction point and main power supply for additional electrical loads, in addition to the starter solenoid feed.

Also connected to the starter solenoid B stud is another large ring terminal, C2, that has two conductors that are part of the engine wiring harness. The first, larger gauge, conductor provides a high amperage electrical path between the generator BAT terminal C1 and the battery. The second, smaller gauge, conductor supplies power to the starter relay circuit in the engine wiring harness.

The starter relay circuit in the engine wiring harness is protected by fusible link M. Fusible link M is spliced at S131, to the conductor that supplies power to the starter relay. Trucks with hydraulic brakes share splice S131 by providing an additional conductor that supplies power to the HYD PUMP fuse in the fuse block 2.

The second smaller gauge battery cable is connected to the fuse block 1 and fuse block 2. with a ring terminal. The fuse blocks each have provisions for six MaxiFuses(R). These MaxiFuses(R) protect the individual electrical circuits and wires that provide power for various electrical components. Most of the MaxiFuses(R) protect electrical circuits and wires that provide power to the convenience center. Several other MaxiFuses(R) protect electrical circuits and wires that provide power to the ignition and starter switch, numerous relays and loads.

The convenience center has up to 29 circuit breakers available that protect electrical circuits and wires that provide power for most of the vehicle's electrical needs.

Additional circuit protection is provided for several other loads. The generator uses an in-line fuse to protect circuits that provide power to the multifunction alarm. On some vehicles, the generator uses the same in-line fuse to protect circuits that provide power to the engine hour meter, and, on vehicles with diesel engines, the instrument panel cluster (IPC).

On all vehicles, an unfused conductor provides a high amperage electrical path between terminal C2 on the starter solenoid BAT stud and terminal C1 on the generator BAT terminal. The circuit has battery voltage when the generator charging output is less than battery voltage. In a properly operating electrical system the generator charging output is greater than battery voltage, and the circuit provides current for maintaining sufficient battery charge.

On vehicles with diesel engines, the generator BAT stud also serves as a junction point to supply power for the engine's air intake heater system. On the generator BAT stud, terminal C1 supplies power to terminal C2, and the circuit is protected by fusible link N. Fusible link N is spliced at S182 and the circuit is connected to the engine.

Some vehicles have a provision for jump-start aid (RPO UEP). This option provides a remote located battery junction block stud that is connected directly to the battery.

Ground is provide at several locations within the IP harness and at several locations within the engine harness.