C.E. Niehoff & Co. C722, C724 Troubleshooting Guides

C722 and C724 Alternator

Troubleshooting Guide

Hazard Definitions

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 – 6

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 w ill increase
several tenths. Amps will increase gradually, then
quickly, to medium to high amps.
— Finally, volts will 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.

• 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 intensi-
ty 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.

TG71A

Page 1

Section A: Wiring Diagrams

CEN C722 Alternator
Description and Operation

C722 28 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. These alternators become externally energized
through the E terminal, connected to a switched power
source to turn on regulator.

Features of A2-212 regulator furnished with some C722
units include:

• R (or W) terminal with voltage limiter
that limits output voltage to
8V peak. Output voltage
frequency (Hz) =
alternator rpm/10.

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

• overvoltage cutout (OVCO).

STATOR

See page 4.

CEN C724 Alternator
Description and Operation

C724 28 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. These
alternators become externally
energized through the IGN terminal,
connected to a switched power source
to turn on regulator.

RECTIFIER

STATOR

*Thermal switch is not factory­installed on all models.

Features of A2-214 regulator furnished with some C724
units include:

• P terminal that can provide
optional AC voltage tap.

• D+ terminal that can provide DC voltage signal to
vehicle electrical system, confirming alternator
operation.

• Overvoltage cutout (OVCO). See page 4.

• Green lens LED. See page 4.

B+

BR

R

R

CHARGE
WARNING
LIGHT OR
CONTROLLER

IGN

DUAL

DIODE TRIO

BK

FIELD

W

*

THERMAL
SWITCH

F
E
D
C
B
A

G

Bñ

B–

ALTERNATOR

Figure 1 — C722 and C724 Wiring Diagrams

IGNITION
SWITCH

E

A2-212
REGULATOR

REGULATOR
RECEPTACLE

LOAD

BATTERY

D+

R

P

R (or W)
terminal

E terminal

Page 2

C722 ADE View

B+ bolt terminal









B– bolt terminal



D+ terminal

Figure 2 — C722 Alternator Terminals

C724 ADE View

IGN terminal

D+ terminal







B+ bolt terminal



B– bolt terminal



Figure 3 — C724 Alternator Terminals

P terminal

TG71A

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 bat-

tery state of charge.

Check: current load on system

is greater than alterna­ tor can produce.

Check: defective wiring or poor

ground path; low regula­ tor 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

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

CAUTION

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,
go to Chart 2, page 5.

TG71A

Page 3

Section C: Advanced Troubleshooting

A2-212 Regulator on C722 Alternator

DESCRIPTION AND OPERATION

A2-212 regulator is attached directly to the outside of
alternator.

Regulators with OVCO (overvoltage cutout) will trip at
vehicle electrical system voltages above 32 volts that
exist longer than 3 seconds. OVCO feature detects
high voltage and reacts by signaling the F+ alternator
circuit to open. This turns off alternator. Restarting
engine resets OVCO circuit. Regulator regains control
of alternator output voltage.

TROUBLESHOOTING

Shut down vehicle and restart engine. If alternator
functions normally after restart, a “no output condi­tion” was 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 5.

A2-214 Regulator on C724 Alternator

DESCRIPTION AND OPERATION

A2-214 regulator is attached directly to the outside of
alternator.

Main diagnostic feature of regulator is a green lens
LED located on the front of the regulator. LED indi­cates whether regulator has been energized. See
Table 2 for LED indication and status.

Regulators with OVCO (overvoltage cutout) will trip at
vehicle electrical system voltages above 32 volts that
exist longer than 3 seconds. OVCO feature detects
high voltage and reacts by signaling the F+ alternator
circuit to open. This turns off alternator. Restarting
engine resets OVCO circuit. Regulator regains control
of alternator output voltage.

TABLE 2—A2-214 Regulator

LED Indications and Status

INDICATION STATUS

ON steady Normal regulator operation.

Alternator is producing output.

FLASHING Regulator is receiving energize

signal. LED will flash until
alternator produces output.

OFF Regulator is not receiving ener-

gize signal or OVCO has tripped.

TROUBLESHOOTING

Shut down vehicle and restart engine. If alternator
functions normally after restart, a “no output condi­tion” was 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 5.

Page 4

TG71A

Section C: Advanced Troubleshooting

(CONT’D)

Chart 1 – C722 and C724 – No Alternator Output – Test OVCO Circuit

With engine off, unplug alternator-to-regulator harness. Connect DMM red lead to pin A on harness plug.
Connect black lead to pin F on same plug. Does resistance measure about 1.2 (± 0.2) ohms?

Yes



Connect DMM red lead to pin A on alternator-to­regulator harness plug. Connect black lead to
alternator B– terminal. Does continuity exist?

Yes



Alternator is defective.

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

Yes

No



Regulator is defective.

Chart 2 – C722 and C724 – No Output

Alternator is defective.

No



No



Repair vehicle harness circuit to IGN or E terminal on
regulator or B+ terminal on alternator.



This step must be performed to obtain

CAUTION

a valid diagnosis of the alternator operation.

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

Yes

No



Retest alternator.



CAUTION

With key off, engine off: Disconnect both jumper wires. Unplug alternator-to-regulator harness. Connect
DMM on DC volt scale across pins C and D 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





Turn off battery switch. Disconnect B+ cable from 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.





Connect 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



Regulator is defective.

Go to Chart 3, page 6.

No



Alternator is defective.

PIN CONNECTIONS

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

Figure 4 – Alternator-to-Regulator Harness Plug

TG71A

Page 5

Section C: Advanced Troubleshooting

(CONT’D)

Chart 3 – Continuation of Chart 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.

Yes



Repair vehicle circuit to E or IGN
terminal. Vehicle charging circuit test
is complete.

USE THIS DIODE

No



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 5 below. Does con­tinuity exist?

Yes



Alternator is
defective.

Thermal switch
in control unit
is defective.

No





Figure 5 – Diode Arrangement inside Drive End Housing

If you have quest ions about your a lternator or any of these test procedures, or if you need to locate a Factory Authori zed Service Dealer, please contact us at:

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

Page 6

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

E-mail us at [e-mail]

TG71A