C.E. Niehoff & Co. N1388-1 Troubleshooting Guides
1300 Series Troubleshooting Guide
for N1388-1 Alternator
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.
Indicates special instructions on
NOTICE
installation, operation or mainte nance that are important but not
related to personal injury hazards.
Table of Contents
Section A: Wiring Diagram .......................................2
Section B: Basic Troubleshooting .............................3
Section C: Advanced Troubleshooting ...................... 4
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 are
lower than regulator setpoint, and amps are
medium.
— 3-5 minutes into charge cycle, system volts
increase and amps decrease.
— 5-10 minutes into charge cycle, system volts
increase to, or near, regulator setpoint, 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 are
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, volts will increase
several tenths. Amps will increase gradually,
then quickly to medium to high amps.
— Finally, volts 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
Voltage and amperage levels are functions of the battery
state of charge. If batteries are in a state of discharge,
as after extended cranking time to start the engine,
system volts when measured after the engine is started
will be lower than the regulator setpoint, and system
amps will be high. This condition is normal for the charging system. 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.
Voltage and amperage readings will change: System voltage reading will increase to regulator setpoint, and system amps will decrease to low level (depending on other
loads) as batteries recover and become fully charged.
• 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 amp value that can cause
battery temperature to rise above adequate charging temperature within 4-8 hours of charge time.
To prevent battery damage, charge amps should be
decreased when battery temperature rises. Check battery manufacturer recommendations on proper rates
of charge amps.
• High Amps: System amp value that can cause battery
temperature to rise above adequate charging temperature within 2-3 hours. To prevent battery damage,
charge amps should be decreased when the battery
temperature rises. Check battery manufacturer recommendations on proper rates of charge amps.
• Battery Voltage: Steady-state volt value measured
with battery in open circuit with no battery load. This
value relates to battery state of charge.
• Charge Voltage: Volt value obtained when charging
system is operating. This value will be higher than
battery voltage and must never exceed the regulator
voltage setpoint.
• B+ Voltage: Volt value obtained when measuring
voltage at battery positive terminal or alternator B+
terminal.
• Surface Charge: Higher-than-normal battery voltage
occurring when battery is removed from battery charger. 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 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: Normal condition which
occurs when the load demand on an alternator is
greater than rated alternator output at given rotor
shaft RPM.
TG0047A
Page 1
Section A: Wiring Diagrams
CEN N1388-1 Alternator
Description and Operation
N1388-1 28 V (300 A) alternator is self-rectifying.
All windings and current-transmitting components
are non-moving, so there are no brushes or slip rings
to wear out. Load-dump protection limits peak voltage
to less than 55 volts during maximum load change
over speed range in batteryless operation. Peak amplitude of voltage including ripple during normal batteryless operation is less than 40 volts. Radio noise suppression is in accordance with Mil-Std 461A, Notice 4
RE05 and CE07.
Ignition switch energizes regulator, and then field coil
is energized. Voltage adjustment is available on alternator control unit.
N3012 regulator furnished with this unit is flat temperature compensated at 28.1±0.15 V at 72 F.
Voltage
adjust plug
receptacle
Figure 1 — N1388-1 Control Assembly
T
Energize
receptacle
T
Regulator
receptacle
T
B+ terminal
Diagnostic
receptacle
T
T
T
T
B– terminal
Figure 2 — N1388-1 Alternator Terminals
(N3012 Regulator Attached to Alternator)
Page 2
Figure 3 — N1388-1 Alternator with N3012 Regulator
TG0047A
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