Progressive Low Voltage Disconnect
Progressive low voltage disconnect (PLVD) shuts off electrical power to selected circuits based on the battery voltage, ignition switch position, and engine running status. There are three groups of circuits with increasing levels of priority for disconnect. PLVD stays at each level for a minimum amount of time to prevent rapid cycling between levels. When PLVD changes its level, the battery voltage may raise slightly due to the reduced load.
When battery voltage drops below a predetermined value, loads designated as comfort loads (priority level I) are shut down first. Then loads designated as house loads (priority level II) are shut down. If necessary, basic loads (priority level III) are shut down last.
PLVD allows the driver to continue using critical loads, while noncritical loads are temporarily unavailable. Calculations for disconnecting loads are based on battery voltage, ignition switch status, and engine rpm. Also, a time delay is implemented for the shutdown and reactivation of loads to avoid unnecessary cycling of loads when battery voltage is close to shutdown thresholds.
One minute before the comfort loads or house loads are shut down, the alarm in the instrument cluster beeps. No alarm sounds before basic loads are shut down.
If the interior lights have been shut down by PLVD, pressing one of the interior light switches (if equipped) brings the interior lights back on.
Note: It is possible to charge a cell phone in an emergency when the truck batteries are low. 12V power receptacles in the main dashboard remain powered in order for cell phone charging during a low voltage emergency.
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12V Power Receptacles
Fig. 1, 12V Power Receptacle, Main Dashboard
Caution: Do not use emergency cell phone charging regularly, This will damage the PLVD strategy for startability during low voltage.
See for the type of loads shut down under specific conditions.
See for the loads that are designated comfort, house, and basic load status.
Table 1, Type of Loads Shut Down Under Specific Conditions
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Type of Loads Shut Down Under Specific Conditions |
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Key Switch Position |
Engine On, Voltage less than 12.5 Volts |
Engine Off, Voltage less than 12.3 Volts |
Engine Off, Voltage less than 12.1 Volts |
|
Off |
N/A |
Priority level I, II loads |
Priority level I, II, and III loads |
|
Accessory |
N/A |
Priority Level I loads |
Priority level I, II loads |
|
On |
Priority level I loads |
Priority Level I loads |
Priority level I, II loads |
|
Start |
N/A |
N/A |
N/A |
Table 1, Type of Loads Shut Down Under Specific Conditions
Table 2, Designated Loads
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Designated Loads |
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Type of Load |
Function |
|
Priority Level I |
12V power receptacle 6 (sleeper, refrigerator) |
|
Amplifier power, accessory |
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|
General sleeper light |
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|
Foot well light |
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|
Reading light 1 (dimmer/theater) |
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|
Reading light 2 (dimmer/theater) |
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|
Rear baggage compartment light |
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|
12V power receptacle 5 (sleeper, cigar), battery |
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|
Auxiliary circulation fan-sleeper, battery |
|
|
12V power receptacle 4 (sleeper, cigar), battery |
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|
Reading light 4 (switched locally), battery |
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|
Priority Level II |
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|
Heated seats, ignition* |
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Sleeper HVAC controller, accessory* |
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|
Cabin HVAC controller, accessory* |
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|
Radio, accessory (clamp 15R) |
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Power feed spare output I, battery |
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|
Power feed spare output III, battery |
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|
Mirror heating, passenger* |
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|
Mirror heating, driver* |
|
|
Power feed spare output IV, battery |
|
|
Power feed spare output II, battery |
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|
Fuel/water separator heater element, ignition* |
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|
Air dryer (pneumatic, electrically heated), accessory* |
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Auxiliary circulation fan-windshield, accessory* |
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Accessory heater power |
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|
Utility light |
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Utility light |
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Dome light rear |
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Area lighting (lower bunk and sleeper work surface), battery |
|
|
Dome light cab, battery |
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|
Overhead compartment lights, battery |
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12V power receptacle 3 (sleeper, cigar), battery |
|
|
Stand-alone HVAC, battery |
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Advertising light, accessory* |
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Dome light passenger |
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Dome light driver/forward overhead |
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|
Priority Level III |
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|
CB radio, battery† |
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|
Fleet management system, battery† |
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|
Trailer power, battery or ignition |
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|
12V power receptacle 2 (dash, phone), battery |
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|
12V power receptacle 1 (dash, cigar), battery |
|
Table 2, Designated Loads
* When the vehicle has Optimized Idle, these functions will not operate with the ignition switch in the accessory position. Optimized Idle may also turn these functions off to reduce stress on the batteries. Refer to the Optimized Idle section in Chapter 11 for more information.
† May or may not shut down depending on how an additional parameter is set at the factory or dealership.