General Description, Vehicle Power Distribution

The vehicle power distribution system provides battery power to the electrical and electronic systems.

The following components make up the vehicle power distribution system:

• Battery Cable Access (BCA)

• Vehicle Power Distribution Module (VPDM)

• Optional Cab Load Disconnect Switch (CLDS)

Vehicle Power Distribution Module (VPDM)

Electronics Bay

VPDM Ground

Battery Cable Access (BCA) Front Wall Pass-Through

VPDM Power

sSAM Ground

sSAM Power

Single System and Actuation Module (sSAM)

Front Wall Cab Ground Pass-Through Stud

Front Wall Interior Ground Stud

Pass-Through Bulkhead Connector

Fig. 1, Cab Power Distribution and Component Location Overview

Vehicle power is supplied by the batteries to the battery cable access (BCA) box. The BCA front wall pass-through is the primary interface through which battery power gets transferred from outside the cab to the inside. It is located on the passenger side of the engine compartment front wall. See Fig..

On vehicles equipped with an optional high current receptacle and/or optional inverter, the BCA will have circuit protection and power cables supplying those devices. Fuse locations will depend on the vehicle and will be outlined on a label on the BCA cover. For an example, see Fig..

Fig. 2, Example Fuse Labeling on BCA Cover

The power supplied by the batteries goes to the vehicle power distribution module (VPDM) and the Single System and Actuation Module (sSAM).

The VPDM is a fuse and relay power distribution box. It provides power and circuit protection for powertrain needs, cab functions, and various stand alone modules. It also supplies power to the emergency power supply circuits in the event of a module failure. The VPDM is located in the vehicle electronics bay, behind the passenger-side dash panel. See Fig..

Depending on a vehicle's specifications, the fuses and relays installed and their locations can vary. Each VPDM cover is illustrated with an image of the fuse and relay layout for that vehicle. See Fig. for an example of VPDM cover map of fuses and relays.

Fig. 3, VPDM Inside Cover Map of Fuses and Relays

Both the VPDM and the sSAM are grounded at the cab-side front wall. See Fig..

On vehicles equipped with a cab load disconnect switch (CLDS), the BCA houses a contacting device that can open to shut off power to high current loads.

The cab load disconnect switch (CLDS) is an optional switch that can be used to open (turn OFF) or close (turn ON) circuits between the battery and the battery cable access box (BCA). It is described more fully later in this chapter.