C.E. Niehoff & Co. N1245, N1248-3 Troubleshooting Guides
C.E. Niehoff & Co.
N1245 and N1248-3
Alternator Troubleshooting Guide
Hazard Defi nitions
These terms are used to bring attention to presence of hazard(s)
of various risk levels or to important information concerning
product life.
Indicates presence of hazard(s) that
will or can cause minor personal
CAUTION
injury or property damage.
Indicates special instructions on
installation, operation or mainte-
NOTICE
nance that are important but not
related to personal injury hazards.
Table of Contents
Section A: Wiring Diagrams ............................... 2 – 3
Section B: Basic Troubleshooting ............................4
Section C: Advanced Troubleshooting ................ 5 – 8
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, amps are medium.
— 3–5 minutes into charge cycle, system volts
increase, 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 characteristics
with slightly longer recharge times.
• Maintenance-free Battery
— Immediately after engine starts, system volts are
lower than regulator setpoint, low charging amps.
— Once charge cycle begins, low volts and low amps
are still present.
— After alternator energizes, voltage will increase
several tenths. Amps will increase gradually, then
quickly, to medium to high amps.
— F i n a l l y , v o l t s w i l l i n c r e a s e t o s e t p o i n t a n d a m p s w i l l
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.
• AGM (Absorbed Glass Mat) Maintenance-free Battery
These dry-cell batteries respond better than standard
maintenance-free. If battery state of charge drops to
75% or less, batteries should be recharged to 95% or
higher separately from the engine’s charging system to
avoid damaging charging system components and to
provide best overall performance. Charge acceptance of
these batteries may display
maintenance batteries.
characteristics similar to
Battery 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 inten-
sity 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.
© 2014, C. E. Niehoff & Co. All rights reserved.
TG44D
Page 1
Section A: Wiring Diagrams
CEN N1245 Alternator
Description and Operation
N1245 28 V (260 A) alternator is internally rectified.
All windings and current-transmitting components are
non-moving, so there are no brushes or slip rings to
wear out. Energize switch activates regulator. Field coil
is then energized.
When controlled by the N3043 regulator, this alternator
becomes self-energizing through internal diode trios.
Residual magnetic field induces small voltage in stator
and energizes field coil. Field coil continues receiving
incremental voltage until full voltage is achieved. AC is
rectified into DC output through diodes. Regulator controls voltage output. N3043 regulator has a D+ terminal
to provide signal to vehicle electrical system, confirming
alternator operation.
When controlled by the N3044 or N3261 regulator,
after engine is running, regulator receives energize
signal through IGN terminal. 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 20 seconds.These regulators are flat temperature
compensated. These regulators have:
• P terminal that can provide optional AC voltage tap.
• D+ terminal to provide optional signal to vehicle
electrical system, confirming alternator operation.
• Tricolored LED on N3261 only. See page 6.
B+ terminal
B– terminal
Figure 1 — N1245/N1248-3 Alternator Terminals
(N3043 Regulator Attached to Alternator)
P terminal
D+ terminal
D+ terminal
CEN N1248-3 Alternator
Description and Operation
N1248-3 28 V (310 A) alternator is internally rectified.
All windings and current-transmitting components are
non-moving, so there are no brushes or slip rings to
wear out. Energize switch activates regulator. Field coil
is then energized.
When controlled by the N3043 regulator, this alternator
becomes self-energizing through internal diode trios.
Residual magnetic field induces small voltage in stator
and energizes field coil. Field coil continues receiving
incremental voltage until full voltage is achieved. AC is
rectified into DC output through diodes. Regulator controls voltage output. N3043 regulator has a D+ terminal
to provide signal to vehicle electrical system, confirming
alternator operation.
IGN terminal
Figure 2 — N3044 Regulator Terminals
P terminal
Figure 3 — N3261 Regulator Terminals
D+ terminal
IGN terminal
Page 2
TG44D
Section A: Wiring Diagrams (CONT’D)
Figure 4 — N1245/N1248-3 Alternator with N3043 Regulator Wiring Diagram
TG44D
Figure 5 — N1245 Alternator with N3044 or N3261 Regulator Wiring Diagram
Page 3
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