C.E. Niehoff & Co. C627, C628, C631, C656, C657 Troubleshooting Guides

C627, C628, C631, C656, C657, C658, C671 and C680

Alternator Troubleshooting Guide

Hazard De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: Alternator Description and Operation . 2–3

Section B: Basic Troubleshooting ............................ 4

Section C: Comprehensive Troubleshooting ......... 5–7

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 with medium amps.
— 3-5 minutes into charge cycle, higher system volts
and reduced amps.
— 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 amps.
— 15-30 minutes into charge cycle, still low volts
and low amps.
— 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 set point 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 set point 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 meas-

ured 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 set point.

• B+ Voltage: A voltage value obtained when measur-

ing voltage at battery positive terminal or alternator
B+ terminal.

• Surface Charge: A higher than normal battery volt-

age 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.

TG30G

Page 1

Section A: Alternator Description and Operation

CEN C656, C657, C658, C671, and C680
Alternator Description and Operation

C656, C657, C658, and C671 14 V (400 A) and
C680 14 V (430 A) alternators are self-rectifying. All

windings and current-transmitting components are
non-moving, so there are no brushes or slip rings to
wear out.

When C656 is controlled by the A2-149 regulator,
this alternator becomes self-energizing through inter­nal diode trios in the drive end housing. Residual
magnetic field induces small voltage in stator and
energizes field coil. Field coil continues receiving
incremental voltage until full voltage is achieved.
See Figure 1. AC is rectified into DC output through
diodes. Regulator controls voltage output. A2-149
regulator has a D+ terminal to provide a signal to
vehicle electrical system, confirming alternator
operation, and an R terminal to provide an optional
AC voltage tap.

When C656, C657, C658, and C680 are controlled by
the A2-155 regulator, these alternators become exter-
nally energized through the IGN terminal connected
to a switched power source to turn on regulator. See
Figure 2. A2-155 regulator has a P terminal to pro­vide an optional AC voltage tap.

Figure 1 — Alternator with A2-149 Regulator

REGUL ATOR

CEN C627, C628, and C631
Alternator Description and Operation

C627 14 V (340A), C628 14 V (290 A), and C631 14 V
(350 A) alternators are self-rectifying. All windings
and current-transmitting components are non-mov­ing, so there are no brushes or slip rings to wear out.

When C627, C628, and C631 are controlled by the
A2-155 regulator, these alternators become externally
energized through the IGN terminal connected to a
switched power source to turn on regulator. See
Figure 2. A2-155 regulator has a P terminal to
provide an optional AC voltage tap. Regulator can be
mounted on the drive end or anti-drive end housing.

Figure 2 — Alternator with A2-155 Regulator

Page 2

TG30G

Section A: Alternator Description and Operation (CONT’D)

A2-149: D+ terminal
A2-155: IGN terminal

B+ terminal stud
(on rear of control unit)









B– terminal stud

Figure 3 — C627/C628/C631/C656/C657

Alternator Terminals

IGN terminal

P terminal





A2-149: R terminal
A2-155: P terminal

B+ terminal stud
(on rear of control unit)



B+
terminal stud

Figure 5 — C671 Alternator Terminals

B+ terminal stud

P terminal





IGN terminal





B– terminal stud

IGN terminal

P terminal





B– terminal stud

Figure 4 — C658 Alternator Terminals

B–
terminal stud

Figure 6 — C680 Alternator Terminals







TG30G

Page 3

Section B: Basic Troubleshooting

Tools and Equipment for Job

• Digital Multimeter (DMM)

• Ammeter (digital, inductive)

• Jumper wires

Identication 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 ACTION

Low Voltage Output

High Voltage Output

No Voltage 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 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 or

regulator.
Check: lost residual magnetism

in self-energizing alternator.
A2-149 regulator: Chart 1
A2-155 regulator: Chart 2

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 trouble­ shooting.

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. In addition, open circuit voltages
must be within ± 0.2 V.

4. Connect meters to alternator
Connect red lead of DMM to alternator B+
terminal and black lead to alternator B– termi­ nal. Clamp inductive ammeter on B+ cable.

5. Operate vehicle

Observe charge voltage.

If charge voltage is above

16 volts, immediately 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 5, for A2-149 regulator or
Chart 2, page 6, for A2-155 regulator.

CAUTION

Page 4

TG30G

Section C: Comprehensive Troubleshooting

Chart 1 – No Output: A2-149 Only

Self-energized alternator may have lost magnetism. Touch steel tool

to shaft to detect any magnetism. Is shaft magnetized?

Yes

Momentarily (1 sec.) jumper D+ terminal on
regulator to B+ terminal on alternator. Touch
shaft with steel tool to detect significant magne­tism. Is shaft magnetized?

No



Yes

Remove jumper from D+ to B+.

No



CAUTION

Unplug alternator-to-regulator harness. Connect DMM across pin D and pin C in
harness plug. Does battery voltage exist?

When conducting this step, ensure that the probes do not touch
other pins, as an arc may damage the wiring in the harness.

Yes No





Alternator is defective.



Set DMM to diode test. Connect black lead of DMM
to pin E in harness plug. Connect red lead to B­terminal or alternator. DMM should read voltage
drop. Reverse leads. DMM should read OL.

Yes

No



Go to Chart 3, page 7.

Install a jumper from B+ terminal on alternator
to pin F in harness plug. Momentarily (1 sec.)
jumper pin A to B– terminal on alternator.
Touch shaft with steel tool to detect significant
magnetism. Is shaft magnetized?

Yes



Install a jumper from B+ terminal on alternator
to pin F in harness plug. Momentarily (1 sec.)
jumper pin A to B– terminal on alternator. Touch
shaft with steel tool to detect significant magne­tism. Is shaft magnetized?

Yes

No

Regulator is defective.





No



Alternator is defective.



Regulator is defective.

TG30G



Alternator is defective.

PIN CONNECTIONS

Pin A F–
Pin B Phase
Pin C B–
Pin D B+
Pin E D+
Pin F F+

Figure 7 – Alternator-to-Regulator Harness Plug

Page 5

Section C: Comprehensive Troubleshooting (CONT’D)

Chart 2 – No Output: A2-155 Only

With engine running, does battery voltage exist at alternator B+ terminal and regulator IGN terminal?

Yes

Repair vehicle harness circuit to IGN terminal on

regulator or B+ terminal on alternator.



CAUTION

With engine off: Unplug alternator-to-regulator harness. Connect DMM across pin D and pin C in harness
plug. Does battery voltage exist?

When conducting this step, ensure that the probes do not touch other pins, as an arc may damage
the wiring in the harness.

Yes No

Alternator is defective.



Turn off battery switch and disconnect B+ battery
cable at alternator. Set DMM to diode test. Connect
black lead of DMM to pin E in harness plug. Connect
red lead to B+terminal on alternator. DMM should
read OL. Reverse leads. DMM should also read OL.

Yes

No





Alternator is defective.

Reconnect B+ battery cable to alternator. Turn on bat­tery switch. Install a jumper from pin F in harness
plug to B+ terminal on alternator. Momentarily (1 sec.)
jumper pin A in harness plug to alternator B– terminal.
Touch shaft with steel tool to detect significant magne­tism. Is shaft magnetized?

Yes



Go to Chart 3, page 7.

Alternator is defective.

No



No





Page 6

PIN CONNECTIONS
Pin A F–
Pin B Phase
Pin C B–
Pin D B+
Pin E D+
Pin F F+

Figure 8 – Alternator-to-Regulator Harness Plug

TG30G

Section C: Comprehensive Troubleshooting (CONT’D)

Chart 3 – Continuation of Chart 1 and 2 as Noted

Set DMM to diode test. Connect black lead of DMM to B+ terminal on alternator. Con­nect red lead to pin B on harness plug. DMM should read voltage drop. Reverse leads.
DMM should read OL.

USE THIS DIODE

Yes



Regulator is defective.

Check continuity of thermal switch inside con­trol unit: Remove drive end cover on alternator.
With DMM, check continuity between pin B on
harness plug and diode shown in Figure 9
below. Does continuity exist?

Alternator is
defective.

No



Yes



No



Thermal switch
in control unit
is defective.



Figure 9 – Diode Arrangement Inside Drive End Housing

If you have que stions ab out your alternator or a ny of these test procedu res, or if you ne ed to locate a Factory Authorized Service Dealer, please contact us at:

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

TG30G

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

E-mail us: service@ CENiehoff.com

Visit our Web site: www.CENiehoff.com

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