C.E. Niehoff & Co. N1387-1 Troubleshooting Guides

N1387 Series Troubleshooting Guide

for N1387-1 Alternators

Hazard Definitions

These terms are used to bring attention to presence of hazards
of various risk levels or to important information concerning
product life.

WARNING

injury, death or substantial property damage if ignored.

CAUTION

injury or property damage if ignored.

NOTICE

nance that are important but not related to personal injury
hazards.

Indicates the presence of hazards
that can cause severe personal

Indicates presence of hazards that
will or can cause minor personal

Indicates special instructions on
installation, operation or mainte-

Table of Contents

Section 1: Component Description .............................. 2

Section 1: Start-up/Shutdown Procedures................... 2

Section 2: Wiring .........................................................3

Section 3: CAN/J1939 Diagnostics .............................. 4

Section 4: Basic Troubleshooting ................................ 5

Section 5: Advanced Troubleshooting ...................... 6-9

Section 6: Troubleshooting the EPM ................... 10-12

Battery Conditions

NOTICE

• Maintenance or low maintenance battery:
— Immediately after engine starts, system volts are

lower than regulator setpoint with medium amps.

— 3-5 Minutes into charge cycle, system volts are

higher and amps are dropping.

— 5-10 Minutes into charge cycle, system volts are

at, or nearly at, regulator setpoint and amps are
reduced to a minimum.

— Low maintenance battery has same characteris-

tics with slightly longer recharge times.

• Maintenance-free battery:
— Immediately after engine start, system volts

are lower than regulator setpoint with low
charging amps.

— 15-30 minutes into charge cycle, volts and amps

are still low.

— 15-30 minutes into charge cycle, volts increase

several tenths. Amps increase gradually, then
quickly, to medium to high amps.

— 20-35 minutes into charge cycle, volts increase

to setpoint and amps decrease.

• High-cycle maintenance-free battery:
— These batteries respond better than standard

maintenance-free. Charge acceptance of these
batteries may display characteristics similar to
maintenance batteries.

Until temperatures of electrical
system components stabilize, these
conditions may be observed during
cold start voltage tests.

Charge Volt and Amp Values

The volt and amp levels are a function of the battery
state of charge. If batteries are in a state of discharge,
as after extended cranking time to start the engine, the
system volts, when measured after the engine is started

will be lower than the regulator setpoint and the system
amps will be high. This is a normal condition for the
charging system. The measured values of system volts
and amps will depend on the level of battery discharge.
In other words, the greater the battery discharge level,
the lower the system volts and higher the system amps
will be. The volt and amp readings will change, system
volts reading will increase up to regulator setpoint and
the system amps will decrease to low level (depending
on other loads) as the batteries recover and become
fully charged.

• Low Amps: A minimum or lowest charging system

amp value required to maintain battery state of
charge, obtained when testing the charging system
with a fully charged battery and no other loads
applied. This value will vary with battery type.

• Medium Amps: A system amps value which can

cause the battery temperature to rise above the
adequate charging temperature within 4-8 hours of
charge time. To prevent battery damage, the charge
amps should be reduced when battery temperature
rises. Check battery manufacturer’s recommenda­tions for proper rates of charge amps.

• High Amps: A system amps value which can cause

the battery temperature to rise above adequate
charging temperature within 2-3 hours. To prevent
battery damage, the charge amps should be reduced
when the battery temperature rises. Check battery
manufacturer’s recommendations for proper rates
of charge amps.

• Battery Voltage: Steady-state voltage value as

measured with battery in open circuit with no
battery load. This value relates to battery state of
charge.

• Charge Voltage: A voltage value obtained when the

charging system is operating. This value will be
higher than battery voltage and must never exceed
the regulator voltage setpoint.

• B+ Voltage: A voltage value obtained when measur-

ing voltage at battery positive terminal or alternator
B+ terminal.

• Surface Charge: A higher than normal battery

voltage occurring when the battery is removed from
a battery charger. The surface charge must be
removed to determine true battery voltage and state
of charge.

• Significant Magnetism: A change in the strength or

intensity of a magnetic field present in the alternator
rotor shaft when the field coil is energized. The
magnetic field strength when the field coil is ener­gized should feel stronger than when the field is not
energized.

• Voltage Droop or Sag: A normal condition which

occurs when the load demand on the alternator is
greater than rated alternator output at given rotor
shaft RPM.

TG0019A

Page 1

Section 1: Component Description and Operation

CEN N1387-1 Dual Voltage Alternator Descrip­tion and Operation

N1387-1 28 V 210 A alternator with optional 28 V/14
V (50 A maximum on 14 V) is internally rectified. All
windings and current-transmitting components are
non-moving, so there are no brushes or slip rings to
wear out.

After engine is running, N3225 regulator receives
energize signal. Regulator monitors alternator
rotation and provides field current only when it
detects alernator shaft rotating at suitable speed.

After regulator detects alternator rotation, it gradu­ally applies field current, preventing an abrupt
mechanical load on accessory drive system. The soft
start may take up to 20 seconds.

N3225 regulator used with these units also

• is negative temperature compensated. Setpoints
are 28.0 ± 0.2 V and 14.0 ± 0.2 V at 75° F.

• provides overvoltage cutout (OVCO). Regulator
will trip OVCO when system voltage rises above
32 V in a 28 V system (16 V in a 14 V system) for
longer than 2 seconds. OVCO feature detects high
voltage and reacts by signaling relay in F– alterna­tor circuit to open, turning off alternator. Restart­ing engine resets OVCO circuit. If vehicle is run in
OVCO mode OVCO will automatically reset when
system voltage drops to 22 V (11 V on 14 V side).
Regulator regains control of alternator below
output voltage.

• maintains alternator output voltage at regulated
settings as vehicle electrical loads are switched
on and off.

• can be used in single or dual voltage with this
alternator.

— Allows single-voltage operation (28 V only).

14 V is not available as a single voltage appli­cation.

— Provides optional 28 V/14 V output only from

the regulator when phase cable from alterna­tor is connected to regulator.

• works with the EPM to provide dual voltage
output during batteryless operation. When
operating in batteryless mode, the system will
have higher ripple. LEDs might change color
more rapidly depending on loads.

EPM Electric Power Manager used with these units

• is rated for continuous current at 200 A on 28 V
side. The 14 V side is rated for continuous
current at 100 A.

• manually connects batteries after battery-connect
button on vehicle is pressed.

• automatically disconnects batteries from vehicle
loads 3 minutes after engine shuts down.

• provides 28 V auxillary output power for up to
four 20 A channels and 14 V auxillary output
power for one 20 A channel, protected by an
internal, resettable, electronic circuit breaker.

• keeps batteries connected to system when emer­gency flashers are used.

Normal Start-Up Procedure

1. Press the vehicle battery-connect button to connect
batteries.

2. Turn START-RUN switch to RUN.

3. Wait until glow plug light goes off.

4. Turn START-RUN switch to START and crank
engine.

5. Return switch to RUN when engine starts.

6. If engine fails to crank, turn START-RUN switch to
OFF, repeat steps 1-5 above.

7. If engine still fails to start, the EPM could be
damaged.

WARNING

a. Remove cables from “Load” side of EPM and

temporarily attach to “Battery” side of EPM.

b. Follow steps 2-5 above.

Do not leave vehicle cabling
connected as described in steps 7a­b. Diagnostic and repair must be
performed as soon as possible.

Emergency Start-Up Procedure

WARNING

1. Connect slave vehicle Nato connector to vehicle.

2. Follow steps 2-5 above.

3. Disconnect slave NATO connector after engine is
running.

This procedure will bypass EPM and
batteries in system. Use this
procedure ONLY when vehicle must
be removed immediately from
location in an EMERGENCY.

Shutdown Procedure

1. Place gear shift in park or neutral and set parking
brake.

2. Turn start-run switch to OFF to stop engine.

3. Batteries will be disconnected from vehicle in 3
min. unless emergency flashers are on, then
batteries will stay connected until flashers are
turned off or battery is discharged.

Page 2

TG0019A

Section 2: Wiring

14 V B+ terminal

IGN terminal

Regulator

AC terminal

diagnostic
LEDs

14 V

TT

T

TT

TT

TT

T

28V

14 V

Figure 1 — N1387-1 Alternator and N3225 Regulator Terminals

TT

T

TT

TT

T

IGN

TT

T

TT

TT

T

TT

TT

28 V B+
terminal

B–

AC

terminal

TG0019A

N3225

REGULATOR

J1939
CONN

Figure 2 — N1387-1 Alternator with N3225 Regulator

Page 3

Section 3: CAN/J1939 Diagnostics

CAN/J1939 Interface

DESCRIPTION AND OPERATION

The EPM and the CEN N3225 digital regulator are compatible with the
SAE J1939 communications standard for vehicle networking.

CEN uses MIL-STD connector MS3112E12-10P to interface between the
EPM/N3225 and the DPA adapter used to monitor the broadcast
messages on the CAN bus line. The readouts of these messages are
shown in Table 2 for the EPM and Table 3 for the regulator.

TABLE 1 – J1939 Connector

Circuit Identification

Pin

A

B

C

D

E

F

G

H

J

K

Identification

CAN High

CAN Low

CAN Shield

Ground

Restricted use

Restricted use

Restricted use

unused

unused

+28V power

Figure 3 – J1939

Connector Pins

T

TT

TT

EPM
Connector
to N3225
Regulator

Figure 4 – EPM Electric Power Manager

T

TT

TT

J1939
Connector
Under Cap

TABLE 2 – EPM/J1939 Readout Diagnostics (With Engine Running)

EPM Readout

Load Voltage 28 V System

Load Voltage 14 V System

Alternator Speed

Battery Voltage 28 V System

Battery Voltage 14 V System

EPM Temperature

Charging and Discharging
Current of 28 V Battery

Batt Charging 28 V LED

Batt Charging 14 V LED

Main Switches On

Cranking Detected

Emergency Flasher Detected

Expected Reading

27–29 V

13.5–14.5 V

1200 to 6000 RPM

27–29 V

13.5–14.5 V

–50ºF (–46ºC) to

200ºF (93ºC)

10 A (varies according

to battery condition)

TABLE 3 – N3225 Regulator/J1939 Readout Diagnostics

Regulator Readout

Alternator Output Voltage 28 V System

Alternator Output Voltage 14 V System

Alternator Speed

Alternator Temperature

Battery Voltage 28 V System

Battery Voltage 14 V System

Alternator Output Capacity

Charging System Status

See Chart 1, page 7.

See Chart 2, page 8.

Check drive belt and charging system connection.

See Chart 1, page 7.

See Chart 2, page 8.

Check connections to EPM.

Observe current charges with battery and ignition on and then off.

OK

OK

OK

OK

OK

See Chart 1, page 7.

See Chart 2, page 8.

Verify “Battery Connect” indicator is lit AMBER.

See Chart 5, page 11.

Check bulbs on flashers or ICC to battery.

Expected Reading

27–29 V

13.5–14.5 V

1200 to 6000 RPM

Less than 260º F/127ºC

27–29 V

13.5–14.5 V

0–100%

OK

Action If Expected Reading Not Achieved

Action If Expected Reading Not Achieved

See Chart 1, page 7.

See Chart 2, page 8.

Check drive belt and chg system connection.

Decrease load on alternator. See Chart 4, page 9.

See Chart 1, page 7.

See Chart 2, page 8.

Varies with load.

See Chart 1, page 7, or Chart 2, page 8.

Page 4

TG0019A