N1200 Series Troubleshooting Guide
for N1224-1/N1224-2/N1224-3 Alternators
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: Regulator Operation Modes ......................... 3
Section 3: CAN/J1939 Operation Modes ...................... 4
Section 4: Basic Troubleshooting ................................. 5
Section 5: Advanced Troubleshooting ......................6 –8
Battery Conditions
Until temperatures of electrical
NOTICE
system components stabilize, these
conditions may be observed during
cold start voltage tests.
• 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.
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 mea-
sured 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 measuring
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.
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Page 1
Section 1: Wiring Diagram
CEN N1224-1/N1224-2/N1224-3 Alternators
Description and Operation
N1224 28 V 260 A/14 V 140 A dual voltage alternator is internally rectified. All windings and currentconducting components are non-moving, so there are
no brushes or slip rings to wear out. Energize switch
(commonly an oil pressure switch or ignition switch)
activates regulator. Field coil is then energized when
rotation is detected. Upper voltage (28 V) is rectified
with standard diodes. Lower voltage (14 V) circuit
output current is controlled by SCRs. Alternator output current is self-limiting and will not exceed rated
capacity of alternator.
N3221 regulator provided with N1224-1 alternator,
N3229 regulator provided with N1224-2 alternator,
and N3232 regulator provided with N1224-3
alternator
• are flat temperature compensated. Setpoint is 28.0
± 1.0 V and 14.0 ± 0.5 V at all temperatures.
• provide 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.
• maintain alternator steady-state output voltage at
regulated settings as vehicle electrical loads are
switched on and off.
In addition, N3232 regulator provided with N1224-3
alternator
• limits alternator output to 200 A.
• automatically determines operating mode (see
Chart 5).
J1939 Data bus connector
Alternator-to-regulator
AC terminal
E terminal
Figure 1 — Alternator and Regulator Terminals
harness
B–
terminal
14 V B+ terminal
T
T
28 V B+ terminal
T
T
T
T
T
Page 2
REGULATOR
Figure 2 — N1224-1 Alternator with N3221 Regulator/N1224-2 Alternator with N3229 Regulator/
N1224-3 Alternator with N3232 Regulator
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Section 2: Regulator Operation Modes
N3221/N3229/N3232 Regulator
DESCRIPTION AND OPERATION
N3221/N3229/N3232 Regulators with OVCO are attached directly to the outside of alternator. Regulator
setpoint has flat temperature compensation. Voltage
setpoint is 28.0 ± 1.0 V and 14.0 ± 0.5.
Once generating power, the alternator will continue
to do so, even if external energize signal is removed.
Once energize signal is removed, the alternator will
shut down approximately 5 seconds after it stops
rotating.
Main diagnostic feature of regulators consists of two
tricolored (red, amber, green) LEDs located on the
side of the regulator. One LED indicates 28 V system
performance, the other LED indicates 14 V system
performance. The two LEDs work independently of
each other. See Table 1 for diagnostic features and
LED explanations.
OVCO (overvoltage cutout) will trip at any of the following conditions:
• 14 V side trips at voltage higher than regulator setpoint that exists longer than 3 seconds of
reading voltage above 16 V. OVCO feature detects
overvoltage and reacts by disabling the alternator
field circuit. This turns off alternator (14 V LED
is steady RED light). OVCO circuit will reset by
either:
— Restarting engine (regulator regains control of
alternator output voltage) OR
— System voltage falling below 11 V. OVCO will
automatically reset.
• 28 V side trips at voltage higher than regulator setpoint that exists longer than 3 seconds of
reading voltage above 32 V. OVCO feature detects
overvoltage and reacts by disabling the alternator
field circuit. This turns off alternator (28 V LED
is steady RED light). OVCO circuit will reset by
either:
— Restarting engine (regulator regains control of
alternator output voltage) OR
— System voltage falling below 22 V. OVCO will
automatically reset.
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, including loose battery cables, both positive
and negative. If battery disconnects from system, it
could cause overvoltage condition in electrical system,
causing OVCO circuit to trip.
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, check color of LED while engine is running.
28 V RED LED - go to Chart 3, page 7.
14 V RED LED - go to Chart 4, page 7.
LED COLOR STATUS
FLASHING
Green
Amber
Red
STEADY
Red
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TABLE 1 – N3221/N3229/N3232 Regulator LED Operation Modes
Regulator is not energized. Measure E terminal voltage. If voltage above 21 V, regulator is defective.OFF
Respective system voltage is at regulated setting and operating under control.
Respective system voltage is below regulated setting. Alternator is not producing power or circuit is
overloaded. See Chart 1 on page 6 for 28 V systems, Chart 2 on page 7 for 14 V systems.
Respective system voltage is above regulated setting. This may occur intermittently with voltage
transients or with system faults.
Alternator is shut down and is not producing power for either voltage. 28 V side trips after
3 seconds of reading voltage above 32 V. 14 V side trips after 3 seconds of reading voltage above
16 V. Regulator remains in this mode until reset by restarting engine or if system voltage drops below
22 V or 11 V, respectively. See Chart 3 on page 7 for 28V systems, Chart 4 for 14 V systems.
Page 3
Section 3: J1939 Operation Modes
CAN/J1939 Interface
DESCRIPTION AND OPERATION
The CEN N3221, N3229, and N3232 digital regulators
are compatible with SAE J1939 communications standard for vehicle networking.
CEN uses MIL-STD connector MS3112E12-10P to interface between the regulator and the vehicle J1939 databus. Mating connector is MS3116E12-10S or equivalent.
If this connection is not used, it must be sealed with
connector cap and chain MS3181-12CA or equivalentsupplied with all regulators. Connector pinout is shown
in Table 2. Message content is shown in Table 4.
TABLE 3 – N3221/N3229/N3232 Regulator—J1939 Readout Diagnostics (see Table 4)
Regulator Readout
Alternator Output Voltage 28 V
Alternator Output Voltage 14 V
Alternator Speed
Regulator Temperature
Alternator Output
Charging System Hours
Expected Reading
27–29 V
13.5–14.5 V
1200 to 8000 RPM
Less than 257 F/125ºC
0–100%
>0 hours
TABLE 2 – J1939 Connector
Circuit Identifi cation
Pin
A
B
C
D
E
F
G
H
J
K
Identifi cation
J1939+
J1939–
J1939/SHLD
Mfr use only
Mfr use only
Mfr use only
Mfr use only
unused
unused
unused
Figure 3 – J1939
Connector Pins
Action If Expected Reading Not Present
See Chart 1, page 6.
See Chart 1, page 6.
Check drive belt and charging system connections.
Decrease load on alternator.
Varies with load.
Check drive belt and charging system connections.
PGN Name 1 2 3 4 5 6 7 8
Table 4 — Message Data (Byte 1 Broadcast after Message ID)
FED5 Alt. Speed ALT RPM
FEF7 Alt. Voltage 24 V OUTPUT 12 V OUTPUT
FEA7 Temperature REG TEMP
FFC8 Proprietary #1ALT
LOAD
Notes:
Unused bytes broadcast as 0xff.
Contact C.E. NIehoff & Co. for definition of custom proprietary message content.
STATUS OVCO TRIP
COUNT
REG HOUR
METER
REG MINS
(0-59)
Page 4
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Section 4: 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 ______________________
T
Regulator model number ______________________
T
C. Preliminary Check-out
Check symptoms in Table 5 and correct as necessary.
TABLE 5 – System Conditions
SYMPTOM
Low Voltage Output
High Voltage Output
No Voltage Output
No 14 V Output
Check: loose drive belt; low bat-
tery state of charge.
Check: current load on system
is greater than alternator
can produce.
Check: defective wiring or poor
ground path; low regulator
setpoint.
Check: defective alternator
and/or regulator.
Check: wrong regulator.
Check: defective regulator.
Check: alternator.
Check: presence of energize
signal.
Check: battery voltage at alterna-
tor output terminal.
Check: defective alternator
and/or regulator.
Go to “Flashing Amber” in
Chart 2, page 7.
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 batter ies 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 5 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 in-
crease within ten minutes, continue to next step.
CAUTION
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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 6.
Page 5
Section 5: Advanced Troubleshooting
Chart 1 – 28 V LED Flashing AMBER – No 28V Alternator Output – Test Charging Circuit
STATIC TEST – MASTER SWITCH ON, KEY ON, ENGINE OFF
Test for battery voltage at alternator 28 V B+ terminal. Does battery voltage exist?
Yes
No
T
Repair vehicle wiring as necessary. Continue test.
T
Jumper 28 V B+ terminal on alternator to E terminal on regulator. Wait 10 seconds. Run engine. Does
alternator charge and is 28 V LED flashing GREEN?
Yes
T
Turn off engine, leave key on. Remove jumper
wire. Go to E terminal on regulator. Test for
battery voltage going into E terminal from battery. Does battery voltage exist?
Yes
No
T
Repair vehicle circuit
to E terminal. Vehicle
charging circuit test is
complete.
T
Run engine and re-test charging
circuit for operation.
T
CAUTION
Turn off engine, leave key on. Connect jumper wire
from pin A in alternator-to-regulator harness plug
to B+ terminal on alternator. Spark will occur.
Touch steel tool to shaft to detect significant magnetism. is shaft magnetized?
Yes
T
No
T
When performing the following
test, connect jumper wire away
from pin A or not at pin A. Spark
may erode pin.
No
T
Alternator is defective.
PIN CONNECTIONS
Pin A F+
Pin B AC
Pin C B–
Pin D 28 V B+
Pin E 14V B+
Pin F Unused
Pin G +14 V Kelvin
Pin H SCR Gate
Figure 4 – Alternator-to-Regulator Harness Plug
T
Set DMM to diode test. Connect DMM red lead to pin C on harness plug. Connect black lead to alternator B+
terminal. Reverse leads. Meter should read OL in one direction, and voltage drop in the other direction. Do tests
prove out?
Page 6
Yes
T
Regulator is defective.
Alternator is defective.
No
T
TG0045A
Section 5: Advanced Troubleshooting (CONT’D)
Chart 2 – 14 V LED Flashing AMBER – No 14 V Alternator Output – Test Circuit
Run engine. Is 28 V LED on regulator flashing GREEN?
Yes
No
T
With engine off, is battery voltage present at alternator 14 V B+ terminal?
Yes
Go to Chart 1.
T
No
Repair vehicle wiring
as necessary. Continue test.
T
T
Connect DMM red lead to pin E on alternator-to-regulator harness plug.
Connect black lead to pin C on same plug. Does battery voltage exist?
Yes
No
T
Alternator is defective.
T
T
Substitute a known good regulator. Run engine. Is regulator setpoint voltage present and is 14 V LED flashing GREEN?
Original regulator was defective.
Chart 3 – 28 V LED Steady RED– No Alternator Output – Test OVCO Circuit
Yes
T
Alternator is defective.
No
T
Remove 28 V and 14 V positive battery cables AT BATTERY PACK before proceeding.
Unplug alternator-to-regulator harness from regulator. Connect red lead from DMM to pin A in plug. Connect black lead to pin C in plug. Does resistance read 1.5 ± 0.2 ohms?
Yes
No
T
Alternator is defective.
T
Reconnect cables. Replace existing regulator with known
good regulator. Run engine. Does OVCO trip?
Yes
No
T
Alternator is defective.
Chart 4 – 14 V LED Steady RED– No Alternator Output – Test OVCO Circuit
Original regulator is defective.
Run engine. Is 28 V LED on regulator flashing GREEN?
Yes
T
T
Replace regulator with known good regulator. Run engine. Does OVCO trip?
Yes
T
Alternator is defective.
Original regulator is defective.
No
T
TG0045A
No
T
Go to Chart 3.
Page 7
Section 5: Advanced Troubleshooting (CONT’D)
Chart 5 – Auto Select of Operating Mode (N3232 Only)
After power up, measure voltage on alternator 14 V output terminal. Is this voltage greater than 5 V?
Yes
T
Alternator will operate in dual voltage mode
with 200 A output limit on 28 V and 140 A output limit on 14 V to a combined total of 200A.
T
Both diagnostic LEDs will flash per Table 1.
No
T
Alternator will operate in single voltage mode
with 200 A output limit on 28 V. No 14 V output.
T
Only 28 V diagnostic LED will flash per Table 1.
If you have questions about your alternator or any of these test procedures, or if you need to locate a Factory Authorized Service Distributor, please contact us at:
TEL: 800.643.4633 USA and Canada • TEL: 847.866.6030 outside USA and Canada • FAX: 847.492.1242
Page 8
C. E. Niehoff & Co.• 2021 Lee Street • Evanston, IL 60202 USA
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