Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter
> Constellation
> Heritage
> 4700 Models
> 4800 Models
> 4900 Models

> 49X
> 5700 Models
> 5900 Models
> 6900 Models

54-057
Western Star
Service Bulletin

Description of Revisions: This bulletin replaces the version dated
6/11/2018. Information about TPPL batteries and testing battery
charge has been added.

IMPORTANT: When troubleshooting powernet issues, use the BCT-460DTNA PowerNet Assessment
Tool. As of May 29, 2018, the AutoMeter® is the only Daimler-approved tool for troubleshooting
vehicle powernet issues.

Using the Powernet Assessment Worksheet
For all battery, charging, or starting issues:
1. Print out the "Powernet Assessment Worksheet," found at the end of this bulletin.
2. Use the "Powernet Worksheet Detail Section" to understand and master the worksheet. The detail section
breaks the worksheet down step by step.
3. Perform each line of the worksheet in order, recording the initial value of each check before performing
repairs. Repair issues as they are found, then recheck. Complete the entire worksheet even if the original
issue seems to be resolved.
4. Once all the checks in the "Powernet Assessment Worksheet" have been completed, if a starting issue
persists, use the "Troubleshooting the Starting System" section near the end of this bulletin.

EPA04/EPA10 and EPA07 Vehicles Require Different Starter Path
Voltage Drop Checks
Two different starter path voltage drop checks are included in the worksheet: an EPA04/EPA10 Check 5, and an
EPA07 Check 5. The alternator cables route through the starter on all vehicles except EPA07, so EPA07
vehicles have a different starter path voltage drop procedure.

NOTE: EPA07 vehicles with jump start posts connected to the starter can be tested using the nonEPA07 (EPA04, EPA10) vehicle procedure by placing the carbon pile clamps on the jump posts
instead of the alternator in check 5a and 5b. Using the jump posts will include them and their cables
to the starter in the voltage drop check.

Western Star Service Bulletin, 10/27/2020

Page 1

54-057

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter

Western Star
Service Bulletin

+

> Constellation
> Heritage
> 4700 Models
> 4800 Models
> 4900 Models

+

−

> 49X
> 5700 Models
> 5900 Models
> 6900 Models

+

+

+

+

−
−

−

−

−

−

−

+

08/16/2013

f151181a

Fig. 1, EPA04, and EPA10 and newer: the alternator
routes through the starter. Use "Starter Path Check —
EPA04, EPA10 Engines" for Check 5.

+

08/16/2013

f151182a

Fig. 2, EPA07: the alternator does not route through
the starter. Use "Starter Path Check — EPA07 Engines"
for Check 5, unless the vehicle has jump posts.

Powernet Worksheet Detail Section (Batteries, Path, Alternator)
BATTERIES CHECK
1.

Check battery pack voltage to determine state of charge.
Charge pack to 100%. If unable, go to 3, "Break pack."

DMM (Digital Multimeter):
POS and NEG batt pack.

Rec
Value

Accept
Value
12.9V TPPL
12.8V AGM
12.6V Flood

Check 1 — Check battery pack voltage to determine state of charge.
If equipped, set Load Disconnect Switch to "Off." With the DMM probes on the positive and negative posts of
the battery pack, record the voltage. Due to differences in their design and operation, flooded cell, AGM, and
TPPL batteries have different voltages at the same state of charge.
Batteries should be fully charged before further testing. If batteries are not fully charged, the test results will be
invalid. Fully charged batteries ensure reliable diagnosis.
See Table 1 for voltage as an approximate indicator of state of charge (SoC) for flooded, AGM, and TPPL
batteries.
If the battery pack will not charge to 100% state of charge, there may be a shorted cell. Break the pack into
individual batteries and test individually using an approved tester. Go to Check 3, Individual Battery Testing.
After batteries have been tested individually, verify pack voltage once again.
Flooded
12.6
12.4
12.3
12.1

Page 2

AGM
(Absorbed Glass Mat)
12.8
12.6
12.4
12.2

TPPL (Thin Plate Pure Lead)
(Odyssey Extreme, NorthStar NSB-AGM31)
12.9
12.6
12.3
12.1

SoC
100%
80%
60%
40%

Western Star Service Bulletin, 10/27/2020

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter
> Constellation
> Heritage
> 4700 Models
> 4800 Models
> 4900 Models

Flooded
12
11.8

Western Star
Service Bulletin

> 49X
> 5700 Models
> 5900 Models
> 6900 Models

AGM
(Absorbed Glass Mat)
12
11.8

54-057

TPPL (Thin Plate Pure Lead)
(Odyssey Extreme, NorthStar NSB-AGM31)
11.8
11.5

SoC
20%
0%

Table 1, Voltage to Approximate State of Charge (SoC)
2.

Remove surface charge: HVAC blower, lights on, 5 min.

Check 2 — Remove surface charge: HVAC blower, lights on, 5 min.
Surface charge refers to a higher initial charge (volts), when discharging, in recently-charged batteries. This
charge is a "shallow" charge, meaning that the charging-induced chemical reaction has mostly occurred at the
surface of the lead plates, and has not equalized throughout the lead. Drawing current from the batteries before
testing removes the surface charge, allowing for a better assessment of the "deep charge" state of the lead
plates.
After the surface charge is removed, the batteries need to be at least 80% SoC for further testing. See Table 1
for voltage as an approximate indicator of state of charge.
3.

Break pack into individual batteries and test each with an approved battery tester.
(Remove NEG cables first!)
Replace batteries if instructed by the tester.
All batteries must pass the battery tester evaluation before troubleshooting continues.

Batt
Batt
Batt
Batt

1:
2:
3:
4:

PASS
PASS
PASS
PASS

or
or
or
or

FAIL
FAIL
FAIL
FAIL

Check 3 - Individual Battery Testing

IMPORTANT: Print and retain the battery test results once the battery test is completed.
Batteries should only be tested individually. If the battery pack had to be charged, let the pack rest a minimum
of 1 hour before testing the batteries.
3.1 Remove the negative cables of the batteries first, and secure the leads out of the way before touching the
positive cables. Remove the battery cables and clean the terminal pads with a wire brush. The tester clamps
will not make sufficient contact with dirty or corroded contact pads.
3.2 Connect the battery tester’s positive and negative clamps to the lead base terminal pads at the positive and
negative studs. See Fig. 3.
The threaded portion of the battery posts are not the right place to clip: the steel threads will not make a good
connection. The base of the post, on the lead, is the best place to clip. Taking a few extra seconds to make
sure the tester, DMM, and carbon pile clips are well-connected can be the difference between a useful and a
useless test.
NOTE: If the lead base is too small to clamp to, only brass stud adapters should be used. Never use steel nuts.
The brass stud adapters must be screwed down tight against the cleaned lead base using a hand tool. Brass
adaptors can be purchased through Paragon using part number DDE AC-107.
Refer to the battery tester instruction manual for complete testing instructions.
If the battery tester requires the CCA rating of the battery, it should be on the battery label. See Fig. 4.

Western Star Service Bulletin, 10/27/2020

Page 3

54-057

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter

Western Star
Service Bulletin

> Constellation
> Heritage
> 4700 Models
> 4800 Models
> 4900 Models

> 49X
> 5700 Models
> 5900 Models
> 6900 Models

02/17/2017
02/17/2017

f151184

f151183

Fig. 3, The lead base of the post is the best place to
clip.

Fig. 4, 3.2 The label has the RC (reserve capacity) CCA
(cold cranking amps) and SERIAL NO. (serial number).

3.3 If the battery fails, enter the battery serial number. See Fig. 4.
PATH CHECK - CABLE VOLTAGE DROP TEST
Alternator Path Check
Carbon Pile:
DMM:
4a. POS alternator, GND alternator. Load at alternator-rated amps. POS alternator, POS batt pack
4b. POS alternator, GND alternator. Load at alternator-rated amps. NEG alternator, NEG batt pack
Combine the voltage from the positive and negative cable drop tests.

Rec
Value

Accept
Value

+
+
=

Total less
than 0.7 V

IMPORTANT: The batteries must be fully charged, and test good with the AutoMeter tool before the
alternator test can be performed. Failure to test with charged batteries may reduce or delay full
alternator output for approximately 15 minutes.
Checks 4a and 4b – Alternator Path Check
Setting up the Carbon Pile
Clip the Carbon Pile positive clamp on the alternator positive post nut, and the negative clamp on the alternator
body.

NOTE: Ground may be on a post, not the body, for some Leece Neville alternators.
Reading Voltage Drop with the DMM
4a - Alternator positive cable and connections voltage drop test
4a.1 Clip one lead of the DMM to the threaded portion of the positive post on the alternator and the other lead
to the positive lead base of one of the batteries. See Fig. 5.
4a.2 The battery pack should now be assembled, cables connected, and nuts tightened 10 to 15 lbf·ft (13 to 20
N·m). The load disconnect switch should be set to "On."
4a.3 Load the system with the carbon pile to the alternator amperage rating for 5 to 10 seconds. Record the
voltage drop shown on the DMM. The DMM should show voltage greater than 0 V. If the DMM displays 0.00 V
when the load is applied, there is a connection problem; check the DMM’s connections and retest.

Page 4

Western Star Service Bulletin, 10/27/2020

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter
> Constellation
> Heritage
> 4700 Models
> 4800 Models
> 4900 Models

54-057
Western Star
Service Bulletin

> 49X
> 5700 Models
> 5900 Models
> 6900 Models

NOTE: The alternator amp rating can be found on the alternator label and in PartsPro. See Fig. 6.

02/17/2017

f151187

Fig. 6, Rated amps can be found on the label.

02/17/2017

f151186

Fig. 5, Alternator Positive Cable Check

4b - Alternator negative cable and connections voltage drop test
4b.1 Clip one lead of the DMM to the alternator body and the other to the negative lead base of one of the
batteries.

NOTE: Ground may be on a post, not the body, for some Leece Neville alternators.
4b.2 Load the system with the carbon pile to the alternator amperage rating. Record the voltage drop shown on
the DMM.
Combine the voltage drop of the positive and negative cable voltage drop tests; the total should not exceed 0.7
V. If total voltage drop is greater than 0.7 V, go to Check 6, then test voltage drop again. If total drop is less
than 0.7 V, go to the next check.
Starter Path Check — EPA04, EPA10 Engines
Carbon Pile:
DMM:
5a. POS alternator, GND alternator. Load at 500 amps.
POS starter, POS batt pack
5b. POS alternator, GND alternator. Load at 500 amps.
NEG starter, NEG batt pack
Combine the voltage from the positive and negative cable drop tests.

Rec
Value
+
+
=

Accept
Value
Total less
than 0.7 V

NOTE: EPA07 vehicles with jump start posts connected to the starter can be tested using this EPA04,
EPA10 vehicle procedure by placing the carbon pile clamps on the jump posts instead of the
alternator in 5a and 5b. Using the jump posts will include them and their cables to the starter in the
drop test.
NOTE: On EPA04 and EPA07 vehicles equipped with a load disconnect switch, expect up to a 0.5 V
drop across the load disconnect switch.
Starter Path Check – Checks 5a and 5b – EPA04, EPA10 Engines
Setting up the Carbon Pile

Western Star Service Bulletin, 10/27/2020

Page 5

54-057

Powernet Troubleshooting Guide: Batteries, Path, Alternator,
and Starter

Western Star
Service Bulletin

> Constellation
> Heritage
> 4700 Models
> 4800 Models
> 4900 Models

> 49X
> 5700 Models
> 5900 Models
> 6900 Models

Clip the carbon pile positive clamp on the alternator positive post and the negative clamp on the alternator body.
See Fig. 7.

NOTE: Ground may be on a post, not the body, for some Leece Neville alternators.
Reading Voltage Drop with the DMM
5a - Starter positive cable and connections voltage drop test
5a.1 Clip the DMM to the threaded portion of the positive post on the starter and the positive lead base of one
of the batteries. See Fig. 8.

IMPORTANT: If the positive alternator cable is smaller than 2/0 AWG, use the "Starter Path Check EPA07" procedure instead.
5a.2 Load the system with the carbon pile at 500 amps. Record the voltage drop shown on the DMM.
5b - Starter negative cable and connections voltage drop test
5b.1 Clip the DMM to the threaded portion of the negative post on the starter and the negative lead base of one
of the batteries.

06/24/2013

f151188

Fig. 7, For EPA04 and EPA10 engines, the starter path
can be checked by loading the circuit at the alternator.

06/24/2013

f151189

Fig. 8, Location of the starter positive post.

5b.2 Load the system with the carbon pile to 500 amps. Record the voltage drop shown on the DMM.
Combine the voltage drop of the positive and negative cable voltage drop tests; the total should not exceed 0.7
V. If total voltage drop is greater than 0.7 V, go to Check 6, then test voltage drop again. If total drop is less
than 0.7 V, go to Check 6 but do not retest voltage drop.
Starter Path Check — EPA07 Engines
Amp Clamp and DMM Location:
5a. Amp clamp around POS starter cable for starter draw.

Page 6

Engine:
Crank engine, under 30 sec.

Rec
Value