C.E. Niehoff & Co. N1335 Troubleshooting Guides
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.
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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
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