Powernet Distribution Box Fuse Retention on the Keep-Alive
Circuit
Constellation
Heritage
> 4700 Models

> 4800 Models
> 4900 Models

> 5900 Models
> 6900 Models

54-60
Western Star
Service Bulletin

SB-10056990-6980
General Information
Some powernet distribution box (PNDB) modules may experience poor fuse retention on the keep-alive circuits.
This could cause intermittent operation of any devices supplied by these circuits. On units equipped with remote
sense, it could result in the alternator overcharging, even on alternators capable of self-regulating.

NOTE: A self-regulating alternator may substitute the voltage reading from its primary battery positive,
in the event that the remote sense line is a constant open circuit.
If the fuses are not seating properly on the keep-alive circuits, or are falling out, use the instructions in this bulletin to replace the PNDB.

PNDB Replacement
NOTE: The powernet distribution box (PNDB) is located on the cab frontwall, above the main ground
junction block. See Fig. 1.
1. Disconnect all batteries. If the vehicle is equipped with an auxiliary battery bank, disconnect these batteries
as well.
2. Open the hood.

IMPORTANT: Inspect the keep-alive and cab load disconnect switch (CLDS) connectors and make
sure that the plugs are in unused connector cavities. Install plugs to seal the connector if any are
missing.
3. Disconnect the cab load disconnect switch (CLDS) connector, if equipped.
4. Disconnect the keep-alive circuit connector from the PNDB.
4.1

Using a flat-head screwdriver, push the red locking tab up.

4.2

Press and release the tab, then remove the connector. See Fig. 2.

5. Disconnect the power cables from the PNDB.
6. Remove the PNDB.
7. Position the new PNDB on the frontwall, and attach the two mounting nuts.
8. Attach the keep-alive circuit connector and the CLDS connector.
9. Connect the power cables. Torque the nut 15 lbf·ft (20 N·m).
10. Connect all batteries, including the auxiliary batteries, if equipped.
11. Close the hood.

Warranty
This procedure is warrantable only if the described condition exists and the repair is performed within the applicable base or extended coverage warranty period. If a failure is not found, this procedure is considered preventive and warranty does not apply.
Normal warranty applies. See Table 1 for OWL VMRS codes and labor allowance information. Enter this service
bulletin number in the Service Bulletin # field.

Western Star Service Bulletin, October 2014

Page 1

54-60

Powernet Distribution Box Fuse Retention on the Keep-Alive
Circuit

Western Star
Service Bulletin

Constellation
Heritage
> 4700 Models

> 4800 Models
> 4900 Models

> 5900 Models
> 6900 Models

1

4
9

8

1

7
2
3
4
11/18/2009

f545618

1. Circuit Connector Locking Tab

6

Fig. 2, Removing the Circuit Connector

5

06/29/2010

1. SAM Cab Power
2. SAM Chassis Power
3. Powertrain PDM
Power
4. Mounting Nut
5. MGJB Ground

f545661

6. Fuse Cover
7. Power (B+)
8. Disconnect Switch
(CLDS) Connector
9. Keep-Alive Circuit
Connector

Fig. 1, Powernet Distribution Box

Primary Failed Part
Powernet Distribution
Box

OWL VMRS Codes and Labor Allowance
Component
Cause Code SRT Code
Description
Code
Powernet Distribution Box, Inspection,
034-004-181
23
285-5025A
R/R

Time: Hours
0.5

Table 1, OWL VMRS Codes and Labor Allowance

Page 2

Western Star Service Bulletin, October 2014