Low Voltage Disconnect
The Low Voltage Disconnect (LVD) system protects the batteries from excessive discharge by disconnecting certain isolated circuits from battery power supply if necessary. See Table.. This allows the batteries to maintain acceptable charge to restart the vehicle. The LVD is integrated into PDM 1. See Fig..
-
PDM 1
-
PDM 2
Fig. 1, Main PDMs
Table 1, Isolated Circuits
|
Isolated Circuits |
|
|
Function |
Key Position |
|
PDM 1 |
|
|
12V Power Receptacle 1, Dash |
OFF/ACC/IGN* |
|
12V Power Receptacle 2, Dash |
OFF/ACC/IGN |
|
12V Power Receptacle 1, Sleeper |
OFF/ACC/IGN |
|
CB Radio |
OFF/ACC/IGN* |
|
Dome Lamp, Cab, Dome/Reading |
OFF/ACC/IGN |
|
Dome Lamp, Sleeper |
OFF/ACC/IGN |
|
Dome Lamp, Floor Lamp, Sleeper |
OFF/ACC/IGN |
|
Fuel Water Separator Heater Element |
IGN |
|
Mirror Heat, Driver |
IGN |
|
Mirror Heat, Hood-Mounted |
IGN |
|
Spare Power Feed 1 |
IGN |
|
Spare Power Feed 2 |
IGN |
|
Utility Lamp |
OFF/ACC/IGN |
|
PDM 2 |
|
|
12V Power Receptacle 2, Sleeper |
OFF/ACC/IGN |
|
12V Power Receptacle 3, Sleeper |
OFF/ACC/IGN |
|
Air Dryer |
ACC |
|
Amplifier Power |
ACC |
|
Sleeper/Cab Auxiliary Heater/Parked HVAC |
OFF/ACC/IGN* |
|
Auxillary Circulation Fan, Windshield |
ACC |
|
Auxilliary/Thermo Coolant Heater |
OFF/ACC/IGN* |
|
Heated Seat |
ACC |
|
Navigation System |
ACC |
|
Optional Switch 1 |
OFF/BAT/IGN† |
|
Optional Switch 2 |
OFF/ACC/IGN† |
|
Optional Switch 3 |
OFF/ACC/IGN† |
|
Optional Switch 4 |
OFF/ACC/IGN† |
|
Optional Switch 5 |
OFF/ACC/IGN† |
|
Optional Switch 6 |
OFF/ACC/IGN† |
|
Optional Switch 7 |
OFF/ACC/IGN† |
|
Optional Switch 8 |
OFF/ACC/IGN† |
|
Optional Switch 9 |
OFF/ACC/IGN† |
|
Optional Switch 10 |
OFF/ACC/IGN† |
|
Radio |
ACC |
|
Refrigerator |
OFF/ACC/IGN* |
|
Sleeper HVAC Controller, Wake-Up |
ACC |
|
Sleeper HVAC Fan Motor |
ACC |
|
Spare Power Feed 3 |
ACC |
|
Spare Power Feed 4 |
OFF/ACC/IGN |
Table 1, Isolated Circuits
* Option to move fuse to remove the function from the LVD bus.
† Option to move fuse to BAT to remove the function from the LVD bus.
If battery voltage drops to the trip point (12.3 or 12.1 volts, determined by the vehicle configuration), the LVD system implements a shut-down. At 70 seconds before the disconnect, an alarm beeps and the low battery indicator light on PDM 1 flashes green. The alarm beeps again at 9 and 3 seconds before the disconnect. If no action is taken, the LVD system will shut off power to the circuits, and a red low battery indicator remains lighted.
These circuits will remain off until the LVD system measures 13.0 volts applied to the system, which can be achieved by starting the engine. After the engine is started, the system will reset.
Vehicles are equipped with an LVD label on the drivers-side sun visor, indicating the presence of the system.