N1335 Alternator
Troubleshooting Guide
Hazard Defi nitions
These terms are used to bring attention to presence of hazards
of various risk levels or to important information concerning
product life.
Indicates presence of hazards that
CAUTION
will or can cause minor personal
injury or property damage if
ignored.
Indicates special instructions on
NOTICE
installation, operation or mainte nance that are important but not
related to personal injury hazards.
Table of Contents
Section 1: Wiring .......................................................... 2
Section 2: CAN/J1939 Diagnostics ............................... 3
Section 3: Basic Troubleshooting ................................. 4
Section 4: Advanced Troubleshooting ..................... 5 - 6
Battery Conditions
Until temperatures of electrical
NOTICE
system components stabilize, these
conditions may be observed during
cold start voltage tests.
• Maintenance/Low Maintenance Battery:
— Immediately after engine starts, system volts
measure lower than regulator setpoint and
system amps measure at a medium level.
— 3-5 minutes into charge cycle, volts increase and
amps decrease.
— 5-10 minutes into charge cycle, volts reach
regulator setpoint or very close, and amps
decrease to a minimum.
— Low maintenance battery has same characteris tics with slightly longer recharge times.
• Maintenance-free Battery:
— Immediately after engine starts, system volts
measure lower than regulator setpoint with low
charging amps.
— Once the charge cycle begins, low volts and low
amps are still present.
— After the alternator energizes, voltage will
increase several tenths. Amps will increase
gradually, then quickly, to medium to high amps.
— Finally, volts will increase to setpoint and amps
will decrease.
The time it takes to reach optimum voltage and amperage will vary with engine speed, load, and ambient
temperature.
• 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.
Charge Volt and Amp Values
Volt and amp levels fluctuate depending on the battery
state of charge. If batteries are in a state of discharge—
as after extended cranking time to start the engine—
system volts will measure lower than the regulator setpoint after the engine is restarted and system amps will
measure higher. This is a normal condition for the
charging system; the greater the battery discharge level,
the lower the system volts and the higher the system
amps. The volt and amp readings will change as batteries recover and become fully charged: system volts will
increase to regulator setpoint and system amps will
decrease to low level (depending on other loads).
• Low Amps: 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: System amps value which can cause
the battery temperature to rise above 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 charge amp rates.
• High Amps: System amps value which can cause
the battery temperature to rise above adequate
charging temperature within 2-3 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 charge amp rates.
• Battery Voltage: Steady-state voltage value as mea-
sured with battery in open circuit with no battery
load. This value relates to battery state of charge.
• Charge Voltage: 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: Voltage value obtained when measuring
voltage at battery positive terminal or alternator B+
terminal.
• Surface Charge: Higher than normal battery voltage
occurring when the battery is disconnected from
battery charger. The surface charge must be removed
to determine true battery voltage and state of charge.
• Significant Magnetism: Change in strength or
intensity of a magnetic field present in 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: Normal condition occurring
when the load demand on alternator is greater than
rated alternator output at given rotor shaft RPM.
TG0052A
Page 1
Section 1: Wiring Diagram
CEN N1335 Alternators
Description and Operation
N1335 28 V 300 A alternators are internally rectified.
All windings and current-conducting components are
non-moving, so there are no brushes or slip rings to
wear out.
After engine is running, N3234 regulator receives energize signal. Regulator monitors alternator rotation and
provides field current only when it detects alternator
shaft rotating at or above idle 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 5 seconds.
N3234 regulator used with these units also
• is negative temperature compensated. Setpoint is
28.8 ± 0.5 V at 72 F when configured to operate with
6TMF type batteries.
• provides overvoltage cutout (OVCO). Regulator will
trip OVCO when system voltage rises above setpoint
by 3 V for longer than 3 seconds. OVCO feature
detects high voltage and reacts by opening alternator
field circuit and turning off alternator. Restarting
engine or waiting until system voltage drops 5 V
below setpoint will reset OVCO circuit.
• maintains alternator steady-state output voltage at
regulated settings as vehicle electrical loads are
switched on and off.
(next to regulator connector)
B+ terminal
T
T
B–
terminal
Figure 1 — N1335 Alternator and
N3234 Regulator Terminals
E terminal
F- terminal
T
T
Page 2
Figure 2 — N1335 Alternators with N3234 Regulator
TG0052A
Section 2: CAN/J1939 Diagnostics
CAN/J1939 Interface
DESCRIPTION AND OPERATION
The CEN N3234 digital regulator is compatible with
SAE J1939 communications standard for vehicle
networking.
CEN uses MIL-C-26482 to interface between the N3234
and the vehicle J1939 databus and battery box sensors.
Mating connector is MS3116E12-10S or equivalent.
If this connection is not used, it must be sealed with
connector cover MS3181-12CA or equivalent. Connector
pinout is shown in Table 1. Message content is shown
in Table 2.
Battery box sensing inputs connect to battery pack
positive terminal (pin J) and battery box thermistor
(pin H). Thermistor is 10K NTC with 32650Ω at 0ºC,
10000Ω at 25ºC, 3601Ω at 50ºC and 1% interchangeability. Thermistor location should be chosen so that it
closely represents battery case temperature. Thermistor
connects between pin H and vehicle chassis, battery
pack negative terminal, or negative bus bar. If either
sensing input (pin H or J) is not used, regulator will
default to internal temperature and alternator voltage.
TABLE 1 – J1939 Connector
Circuit Identifi cation
Pin
A
B
C
D
E
F
G
H
J
K
Identifi cation
J1939+
J1939 –
J1939/SHLD
B–/GND
Mfr use only
Mfr use only
Mfr use only
Ext. Temp. Sense
Ext. Voltage Sense
unused
Figure 3 – J1939
Connector Pins
TABLE 2 – N3234 Regulator/J1939 Readout Diagnostics (see Table 3)
Regulator Readout
Alternator Speed
Alternator Voltage
Battery Voltage
Regulator Temp.
Alternator Current
Alternator Load
Battery Temp.
Stator Voltages
Expected Reading
1500 to 8000 RPM
26 to 30 V (when charging)
26 to 30 V (when charging)
–40 to 125ºC
0 to 300 A
0 to 100%
–40 to 80ºC
10 to 18 V (when charging)
Check belts and pulley.
Check alternator drive and regulator IGN signal.
Check battery box voltage sense signal.
Check regulator.
Check alternator output cabling.
Check alternator output cabling.
Check battery box thermistor.
Check alternator belts and output.
Action If Expected Reading Not Present
Table 3 — Message Data
PGN Name 1 (1) 23 4 5 6 7 8
FED5 Alt. Speed Alt. RPM
FEF7 Alt. Voltage Alt. Voltage Batt. Voltage
FEA7 Alt. Temp. Alt. Temp.
FFC8 Proprietary #1 Warning Light Regulator Hrs. Load Batt. Temp.
FFC9 Proprietary #2 OVCO Count Software Version
Notes:
(1) Byte 1 broadcast closest to CAN frame ID.
TG0052A
Page 3
Section 3: Basic Troubleshooting
A. Tools and Equipment for Job
• Digital Multimeter (DMM)
• Ammeter (digital, inductive)
• Jumper wires
B. Identifi cation Record
List the following for proper troubleshooting:
Alternator model number _________________________
U
Regulator model number ________________________
U
C. Preliminary Check-out
Check symptoms in Table 4 and correct as necessary.
TABLE 4 – System Conditions
SYMPTOM
Low Voltage Output
High Voltage Output
No Voltage Output
Check: loose drive belt;
low battery state of charge.
Check: current load on system
is greater than alternator
can produce.
Check: defective wiring or poor
ground path.
Check: defective alternator
and/or regulator.
Check: defective regulator.
Check: alternator.
Check: presence of energize sig-
nal to E terminal on regulator.
Check: battery voltage at alter-
nator output terminal.
Check: defective alternator
and/or regulator.
ACTION
D. Basic Troubleshooting
1. Inspect charging system components
Check connections at ground cables, positive
cables, and regulator harness. Repair or replace
any damaged component before troubleshooting.
2. Inspect connections of vehicle batteries
Connections must be clean and tight.
3. Determine battery type, voltage, and state
of charge
Batteries must be all the same type for system
operation. If batteries are discharged, recharge
or replace batteries as necessary. Electrical system
cannot be properly tested unless batteries are
charged 95% or higher. See page 1 for details.
4. Connect meters to alternator
Connect red lead of DMM to alternator B+
terminal and black lead to alternator B–
terminal. Clamp inductive ammeter on B+
cable.
5. Operate vehicle
Observe charge voltage.
If charge voltage is above
33 volts, immediately shut
down system. Electrical
system damage may occur
if charging system is
allowed to operate at
excessive voltage. Go to
Table 4 at left.
If voltage is at or below regulator setpoint, let
charging system operate for several minutes to
normalize operating temperature.
6. Observe charge volts and amps
Charge voltage should increase and charge amps
should decrease. If charge voltage does not
increase within ten minutes, continue to next step.
7. Batteries are considered fully charged if charge
voltage is at regulator setpoint and charge amps
remain at lowest value for 10 minutes.
8. If charging system is not performing properly,
go to Chart 1, page 5.
CAUTION
Page 4
TROUBLESHOOTING
Shut down vehicle and restart engine. If alternator
functions normally after restart, a “no output condition”
was normal response of voltage regulator to overvoltage
condition. Inspect condition of electrical system.
If you have reset alternator once, and electrical system
returns to normal charge voltage condition, there may
have been a one time, overvoltage spike that caused
OVCO circuit to trip.
If OVCO circuit repeats cutout a second time in short
succession and shuts off alternator field circuit, try
third restart. If OVCO circuit repeats cutout a third
time, go to Chart 1, page 5.
TG0052A
Section 4: Advanced Troubleshooting
Chart 1 – No Alternator Output – Quick Diagnostic
With engine running: Does battery voltage exist at alternator B+ terminal and regulator IGN terminal?
Yes
Repair vehicle harness circuit to IGN terminal on regulator
or B+ terminal on alternator.
T
With key off, engine off: Does battery voltage exist at alternator B+ terminal?
Yes
Repair vehicle harness circuit to B+ terminal on alternator.
T
With key off, engine off: Unplug alternator-to-regulator harness at alternator and regulator connectors. Check for
continuity at both ends of harness. Does continuity exist at each pin-to-pin?
No
T
No
T
Yes
No
T
Harness is defective.
T
Plug in alternator-to-regulator harness at regulator connector. Connect DMM on DC volt scale across pins C and D
at alternator connector. Does battery voltage exist?
Yes
No
T
Alternator is defective.
T
With DMM on resistance scale, does field resistance between pins F and A in harness plug measure ~1.4 (±0.2)Ω?
Yes
No
T
Alternator is defective.
T
Set DMM to diode test. Check continuity of rear stator diodes: Connect red lead to pin B in harness plug. Connect
black lead to alternator B+ terminal. Meter should read one diode drop (approx. 0.6 to 0.9 V). Disconnect leads.
Connect red lead to alternator B– terminal. Connect black lead to pin B. Meter should read one diode drop (approx.
0.6 to 0.9 V).
Yes
No
T
T
Alternator is defective.
Set DMM to diode test. Check continuity of front stator diodes: Connect red lead to pin H in harness plug. Connect
black lead to alternator B+ terminal. Meter should read one diode drop (approx. 0.6 to 0.9 V).
Disconnect leads. Connect red lead to alternator B– terminal. Connect black lead to pin H. Meter should read one
diode drop (approx. 0.6 to 0.9 V).
Yes
T
Go to Page 6 to continue.
Figure 4 – Alternator-to-Regulator Harness Plug
PIN CONNECTIONS
Pin A F–
Pin B Phase 1
Pin C GND/B–
Pin D B+
Pin E Kelvin +
Pin F F+
Pin G Kelvin –
Pin H Phase 2
Alternator is defective.
No
T
TG0052A
Page 5
Section 4: Advanced Troubleshooting
(CONT’D)
Chart 1 cont’d from Page 5 – No Alternator Output – Quick Diagnostic
With DMM on resistance scale: Connect red lead to pin E in harness plug. Connect black lead to alternator B+
terminal. Meter should read 0 ohms. Change pin E to pin G. Meter should read 0 ohms.
Yes
Alternator is defective.
T
Momentarily (1 sec.) jumper pin F in harness plug to alternator B+ terminal and jumper pin A in harness plug to
B- terminal. Touch shaft with steel tool to detect significant magnetism. Is shaft magnetized?
No
T
Yes
T
Regulator is defective.
Figure 5 – Alternator-to-Regulator Harness Plug
PIN CONNECTIONS
Pin A F–
Pin B Phase 1
Pin C GND/B–
Pin D B+
Pin E Kelvin +
Pin F F+
Pin G Kelvin –
Pin H Phase 2
No
T
Alternator is defective.
If you have questions about your alternator or any of these test procedures, or if you need to locate a Factory Authorized Service Dealer, please contact us at:
C. E. Niehoff & Co.• 2021 Lee Street • Evanston, IL 60202 USA
TEL: 800.643.4633 USA and Canada • TEL: 847.866.6030 outside USA a nd Canada • FAX: 847.492.1242
Page 6
TG0052A
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