C.E. Niehoff & Co. C612, C617, C621, C624 Troubleshooting Guides

C.E. Niehoff & Co.

C612/C617/C621/C624 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.

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 – 3

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

Section C: Advanced Troubleshooting ...................... 5

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 Batter y
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.

TG2D

Page 1

Section A: Wiring Diagrams

CEN C612/C617/C624 Alternators
Description and Operation

C612/C617/C624 28 V (240 A) alternators are
self-rectifying and self-energized. All windings and
current-transmitting components are non-moving,
so there are no brushes or slip rings to wear out.

R or P Terminal

D+ Terminal

B+ Terminal







B– Ground Bolt

Figure 1 — C612/C617 Alternator Terminals



When controlled by the A2-141 regulator, these alterna-
tors become 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. Regulator has:

• D+ terminal to provide a signal to vehicle electrical
system, confirming alternator operation

• P terminal to provide an optional AC voltage tap.

D+ terminal

B+ terminal

B– terminal
on other side
of alternator

Figure 2 — C624 Alternator Terminals

P terminal

Page 2

BK

BR

R

W

G

Figure 3 — C612/C617/C624 Alternator Wiring Diagram

TG2D

Section A: Wiring Diagrams (CONT’ D)

CEN C621 Alternator
Description and Operation

C621 28 V (220 A) alternators are self-rectifying and
self-energized. All windings and current-transmitting
components are non-moving, so there are no brushes or
slip rings to wear out.

When controlled by the A2-141 regulator, these alterna-
tors become 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. Regulator has:

• D+ terminal to provide a signal to vehicle electrical
system, confirming alternator operation

• P terminal to provide an optional AC voltage tap.

R or P Terminal

D+ Terminal

B+ Terminal





B– Ground Bolt

Figure 4 — C621 Alternator Terminals





BR

R

BK

W

G

TG2D

Figure 5 — C621 Alternator Wiring Diagram

Page 3

Section B: Basic Troubleshooting

Tools and Equipment for Job

• Digital Multimeter (DMM)

• Ammeter (digital, inductive)

• Jumper wires

• CEN Regulator Bypass Adapter A10-129

Identifi 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

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

or regulator.

Check: wrong regulator.

Check: high regulator setpoint.

Check: defective regulator.

Check: alternator.

Check: broken drive belt.

Check: battery voltage at alternator

output terminal.

Check: defective alternator

or regulator.

Check: lost residual magnetism in

self-energizing alternator.
Go to Chart 1, page 5.

Failure to check for the following

NOTICE

conditions will result in erroneous
test results in the troubleshooting
charts.

Basic Troubleshooting

1. Inspect charging system components for damage
Check connections at B– cable, B+ cable, and
regulator harness. Also check connections at
regulator terminal wiring from regulator to vehicle
components. Repair or replace any damaged
component before electrical troubleshooting.

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

3. Check drive belt
Repair or replace as necessary.

4. Determine battery voltage and state 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.

5. 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.

6. Operate vehicle

Observe charge voltage.
If charge voltage is above

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

If voltage is at or below regulator setpoint, let

charging system operate for several minutes to
normalize operating temperature.

7. 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.

8. Battery is considered fully charged if charge
voltage is at regulator setpoint and charge amps
remain at lowest value for 10 minutes.

9. If charging system is not performing properly,

CAUTION

go to,Chart 1, page 5.

Page 4

TG2D

Section C: Advanced Troubleshooting

Chart 1 – No Output

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





Unplug alternator-to-regulator harness. Connect
DMM across socket A and socket E in harness plug.
Does battery voltage exist?

Yes

No



Alternator is defective.



Set DMM to diode test. Connect black lead of DMM
to socket B 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.



Set DMM to Diode Test. Connect DMM red lead to
socket D on alternator-to-regulator harness plug.
Connect black lead to alternator B+ terminal.
Does continuity exist?

Yes No





Yes

No



Remove jumper from D+ to B+.



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

Yes

No



Alternator is defective.

SOCKET CONNECTIONS
A B–
B Field +
C Field –
D AC
E B+



Alternator is defective.



Regulator is defective.

If you have questions about your a lternator or a ny of these test procedures, or if you need to locate a Factory Authorized Service Dealer, please contact us at:

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

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

E-mail us at [e-mail]

TG2D

Figure 6 – Alternator-to-Regulator Harness Plug

Page 5