C.E. Niehoff & Co. N1380-2 Troubleshooting Guides

1300 Series Troubleshooting Guide

for N1380-2 Alternator

Hazard Definitions

These terms are used to bring attention to presence of hazards
of various risk levels or to important information concerning
product life.

CAUTION

NOTICE

Indicates presence of hazards that
will or can cause minor personal
injury or property damage.

Indicates special instructions on
installation, operation or mainte­nance 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

NOTICE

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.

Until temperatures of electrical
system components stabilize, these

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.

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Page 1

Section A: Wiring Diagrams

CEN N1380-2 Alternator
Description and Operation

N1380-2 28 V (220 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. Ignition switch energizes regulator.
Field coil is then energized.

N3109 regulator used with these units:

• is negative temperature compensated for 28.3
± 0.1 V at 72º F for temperature variation
at –0.1 volt per 10º F.

• provides overvoltage cutout (OVCO). Regulator
will trip OVCO when system voltage rises above
32 V for longer than 2 seconds. OVCO feature
detects high voltage and reacts by signaling relay
in F– alternator circuit to open, turning off
alternator. Restarting engine resets OVCO circuit.

Regulator
receptacle

TT

T

TT

T

TT

Figure 1 — N1380-2 Alternator Terminals

TT

Output receptacle

TT

T

TT

B– terminal
bolt

Page 2

Figure 2 — N1380-2 Alternator with N3109 Regulator

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Section B: Basic Troubleshooting

Tools and Equipment for Job

• Digital Multimeter (DMM)

• Ammeter (digital, inductive)

• Jumper wires

Identification Record

List the following for proper troubleshooting:

Alternator model number ____________________

❏

Regulator model number _____________________

❏

Setpoints listed on regulator __________________

❏

Preliminary Check-out

Check symptoms in Table 1 and correct if necessary.

TABLE 1 – 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; low regulator
setpoint.

Check: defective alternator and/

or regulator.
Check: wrong regulator.
Check: high regulator setpoint.
Check: defective regulator.
Check: alternator.
Check: broken drive belt.
Check: battery voltage at alter-

nator output terminal.
Check: defective alternator

and/or regulator.

ACTION

Basic Troubleshooting

1. Inspect charging system components for

damage

Check connections at B– cable, B+ cable, and
alternator-to-regulator harness. Repair or
replace any damaged component before trouble­shooting.

2. Inspect all vehicle battery connections
Connections must be clean and tight.

3. Determine battery voltages and states of

charge

If batteries are discharged, recharge or replace
batteries as necessary. Electrical system cannot
be properly tested unless batteries are charged
95% or higher.

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.

CAUTION

shut down system. Electrical system damage may occur if
charging system is allowed to operate at high voltage. Go to
Table 1 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 4.

9. Check OVCO circuit
Shut down vehicle and restart engine. If alterna­tor functions normally after restart, a “no output
condition” was a normal response of voltage
regulator to “high voltage” condition. Inspect
condition of electrical system, including loose
battery cables, both positive and negative. If
battery disconnects from system, it could cause
“high voltage” 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, high volt­age spike, causing OVCO circuit to trip.

If OVCO circuit repeats cutout a second time in
short succession and shuts off alternator F–
circuit, try third restart. If OVCO circuit repeats
cutout, go to Chart 1, page 4.

If charge voltage is above
33 volts, immediately

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Page 3

Section C: Advanced Troubleshooting

Chart 1 – No Output

Ignition switch on, engine off: Check for battery voltage between B–
terminal on alternator and Pin A on output receptacle (back-probe pin).

Ye s

TT

T

TT

Ignition switch off: Back-probing pins, momentarily (1 sec.) jumper
Pins A and B in the output receptacle. Touch shaft with steel tool
to detect any magnetism. Is shaft magnetized?

Yes

TT

T

TT

Check ignition switch
and vehicle wiring.

Disconnect regulator harness and output harness. Perform series
of tests with DMM:

No

TT

T

TT

1) With meter set on diode test, connect red lead to pin C of output
receptacle and black lead to pin D of regulator receptacle. Meter
should read continuity. Reverse leads. Meter should read OL.

2) With meter set on ohms, check field coil resistance across
pins A and D of regulator receptacle. Resistance should measure
less than 3 ohms.

3) With meter set on ohms, check for continuity between pin C of
regulator receptacle and B– terminal on alternator.

Did all three tests provide correct readings?

Ye s

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Regulator is defective.

No

TT

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Repair vehicle wiring to
output receptacle.

No

TT

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TT

Alternator is defective.

PIN CONNECTIONS

Figure 3 – Regulator 5-pin Receptacle

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: [phone] USA and Canada • TEL: [phone] outside USA and Canada • FAX: [phone]

Page 4

Pin A Field –
Pin B Energize
Pin C Ground
Pin D B+
Pin E Not Used

C. E. Niehoff & Co.• 2021 Lee Street • Evanston, IL 60202 USA

Figure 4 – Output 3-pin Receptacle

E-mail us at [e-mail]

PIN CONNECTIONS

Pin A B+
Pin B Energize
Pin C Phase

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