Electrical Systems


Electrical System General Information

The Saf-T-Liner C2 uses an electrical system where multiple electrical signals are carried along a simplified set of wires, reducing the size of wiring bundles. There are significantly fewer wires overall, meaning less chance of damage, shorts, and other problems. The information in this chapter is to help familiarize the driver with the basic electrical system. Servicing the electrical system requires special skills and equipment and should only be performed by a qualified technician. Take the vehicle to an authorized Thomas Built Bus dealer when service is needed.

Power Distribution Modules

There are two power distribution modules (PDAs).
The main PDM is located under the hood on the driver's side above the fender. See Fig. 8.1 . The main PDM distributes battery power to the vehicle's control modules, and contains the fuses required to protect the power feed circuits to these modules. While the main PDM provides power to the modules, the modules themselves control power flow and circuit protection to the various components of the vehicle's electrical systems. Because of this, traditional PDM devices such as relays and circuit breakers are no longer necessary on the main PDM.
Inside the lid of the fuse box there is a sticker that shows the location of the fuses and describes the circuit(s) that each fuse protects. Fuse configuration will vary depending on the PDM assembly installed. See Fig. 8.2 . See Table 8.1 for descriptions of a typical set of fuses.
The cab PDM is located in the switch panel cavity at the driver's left elbow and handles circuits inside the vehicle, such as heaters, doors, fans, lights, and other interior accessories. See Fig. 8.3 .
Because the electrical system is multiplexed, no relays are needed. The multiplexing module performs the functions normally provided by relays.
Fuse Identification
CAV
Description
Fuse
F1
VCU (spare)
10A (—)
F2
Blower Motor
30A
F3
Engine ECU
20A
F4
RR Wall HTR RLY LO/HI
30A
F5
Ignition Switch
10A
F6
Hydromax RLY (spare)
30A (—)
F7
Stepwell HTR RLY LO/HI
30A
F8
ICU3-M2
10A
F9
Transmission ECU
10A
F10
Expansion Module 1
30A
F11
Expansion Module 1
30A
F12
Radio/Diagnostic
20A
F13
Expansion Module 1
30A
F14
Expansion Module 2
30A
F15
Bulkhead Module
30A
F16
ABS ECU
15A
F17
Chassis Module
30A
F18
Bulkhead Module
30A
F19
Chassis Module
30A
F20
Bulkhead Module
30A
F21
Expansion Module 2
30A
F22
Bulkhead Module
30A
F23
Expansion Module 2
30A
F24
Hydraulic Pump and RLY (spare)
25A (—)
F25
Adjustable Pedals
10A
F26
Chassis Module
30A
F27
Heater Booster Pump
20A
F28
Bulkhead Module
30A
F29
Crossing Arm RLY
10A
Table 8.1, Main PDM Fuse Identification
  • 1. Bulkhead Module
  • 2. Main PDM
Fig. 8.1, Location of the Main PDM
  • 1. Battery Power Mega Fuse 1
  • 2. Battery Power Mega Fuse 2
  • 3. Engine Harness (green)
  • 4. Forward Chassis Harness (blue)
  • 5. Forward Chassis Harness (gray)
  • 6. Frontwall Harness (black)
Fig. 8.2, Main PDM
Fig. 8.3, Cab PDM