C.E. Niehoff & Co. C626 Troubleshooting Guides

C.E. Niehoff & Co.

C626 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

Section B: Basic Troubleshooting .............................3

Section C: Advanced Troubleshooting ................ 4 – 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.

TG67B

Page 1

Section A: Wiring Diagrams

CEN C626 Alternators
Description and Operation

C626 28 V (260 A) alternator is self-rectifying and self­energized. All windings and current-transmitting
components are non-moving, so there are no brushes
or slip rings to wear out.

When controlled by the A2-337 regulator, the alternator
becomes self-energized through sensing of alternator
rotation through AC circuit. Residual magnetic field
induces small voltage in stator and energizes field coil.
Field coil continues receiving incremental voltage until
full voltage is achieved. Regulator controls voltage out­put. See wiring diagram, Figure 2. A2-337 regulator
has:

• P terminal that can provide optional AC voltage tap.

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

• Tricolored LED. See page 4.

• T terminal to connect optional A9-4011 temperature
sense lead to adjust regulator setpoint to maintain
charge voltage (or negative temperature compensa­tion) by sensing ambient temperature within the
battery box. If temperature sense lead is not
connected, regulator uses setpoint switch on the
back of the regulator to keep a constant setpoint
(or flat temperature compensation).

When controlled by the A2-141 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. Regulator has:

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

• P terminal to provide an optional AC voltage tap.

P
terminal

D+ terminal

Figure 1 — C626 Alternator Terminals

T terminal
(A2-337 only)

B+ terminal

B– terminal

Page 2

Figure 2 — C626 Alternator with A2-141 or A2-337 Regulator



T
(A2-337 only)

LED
(A2-337 only)

TG67B

Section B: Basic Troubleshooting

Tools and Equipment for Job

• Digital Multimeter (DMM)

• Ammeter (digital, inductive)

• Jumper wires

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.

TG67B

Page 3

Section C: Advanced Troubleshooting

A2-337 Regulator
Description and Operation

A2-337 regulator is attached directly to the outside of
alternator. A9-4011 temperature sense lead may or may
not be used with this regulator. See below.

Main diagnostic feature of the regulator is a tricolored
LED next to the harness receptacle on regulator. LED
works like a voltmeter, measuring charging voltage. See
Table 2 for diagnostic features and LED explanations.

When the A9-4011 temperature sense lead is not in use,
the regulator will operate at 27.5 V.

When A9-4011 temperature sense lead is in use, the
lead senses the ambient temperature within the battery
box and regulator will adjust charge voltage based on
battery temperature—the higher the battery tempera­ture, the lower the charge voltage.

LED COLOR STATUS

GREEN Solid

Flashing

AMBER Solid

Flashing

RED Solid

Page 4

TABLE 2 – A2-337 Regulator Diagnostics

Alternator and regulator operating normally.

Regulator is in soft start mode.

Low system volta ge — Electrical load exceeds
alternator rating at present rotor speed.

Alternator fault — No output.

High system voltage.

ACTION

No action required.

Wait 10 seconds until a lternator achieves full
rotation.

When loads decrease or speed increases, LED
should be solid GREEN. If not, check drive belt
and charging system connections.

Replace alternator.

May occur during normal load switching.

TG67B

Section C: Advanced Troubleshooting (CONT’D)

Chart 1 – A2-337 & A2-141 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]

TG67B

Figure 4 – Alternator-to-Regulator Harness Plug

Page 5