C.E. Niehoff & Co.
C653/C653A and C625 Alternators
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: A2-146/A2-153 Troubleshooting ..............5
Section D: A2-214 Troubleshooting .................... 6 – 9
Section E: C653 w/A2-338 Troubleshooting ... 10 – 11
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.
TG13G
Page 1
Section A: Wiring Diagrams
CEN C653/C653A and C625 Alternators
Description and Operation
C653/C653A and C625 28 V (260 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 controlled by the A2-146 or A2-153 regulator,
these alternators 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.
When controlled by the A2-214 regulator, these alter-
nators become externally energized through the IGN
terminal, connected to a switched power source to turn
on regulator. See wiring diagram, Figure 5 on page 3.
Regulator has:
• D+ terminal that can provide signal to vehicle
electrical system, confirming alternator operation.
• P terminal that can provide an optional AC voltage
tap.
• Overvoltage cutout (OVCO). See page 6.
• Green lens LED. See page 6.
When C653 alternator is controlled by the A2-338
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 4 on page 3. A2-338 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.
• Overvoltage cutout (OVCO) function. See page 10.
• Tricolored LED. See page 10.
• 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, the regulator will operate at 27.5 V.
B+ terminal stud
B– terminal
stud
Figure 2 — A2-146 and A2-153 Regulator Terminals
P
terminal
T terminal
(A2-338 only)
IGN terminal
Figure 1 — C625 Alternator Terminals
(Also Used with C653, C653A)
B– terminal
stud
R terminal
D+ terminal
D+ terminal
IGN terminal
(A2-214 only)
P
terminal
D+ terminal
B+ terminal
stud
(on rear of
control unit)
Page 2
C653
ADE View
Figure 3 — C653/C653A Alternator Terminals
C653A
ADE View
TG13G
Section A: Wiring Diagrams (CONT’ D)
P or R
*
REGULATOR
LED
(A2-338 only)
*Thermal switch is not
factory-installed on all models.
T
(A2-338 only)
Figure 4 — C653/C653A Alternators with A2-146 or A2-153 or A2-338 Regulator
IGN
TG13G
*
*Thermal switch is not
factory-installed on all models.
Figure 5 — C653/C653A and C625 Alternators with A2-214 Regulator
LED
P
Page 3
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, for
A2-146/A2-153
• Chart 2, page 7, for
A2-214
• Chart 5, page 11, for
A2-338
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,
go to:
• Chart 3, page 8, for A2-214
• Chart 5, page 11, for A2-338
CAUTION
• Chart 1, page 5, for A2-146/A2-153
Page 4
TG13G
Section C: A2-146/A2-153 Advanced Troubleshooting
A2-146/A2-153 REGULATOR – THIS PAGE ONLY
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
CAUTION
Unplug alternator-to-regulator harness. Connect
DMM across pin D and pin C in harness plug.
Does battery voltage exist?
Yes
When conducting this step,
ensure that the probes do not
touch other pins, as an arc
may damage the wiring in the
harness.
No
Alternator is defective.
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.
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
Alternator is defective.
Regulator is defective.
Yes
No
Remove jumper from D+ to B+.
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
Alternator is defective.
Regulator is defective.
PIN CONNECTIONS
Pin A F–
Pin B Phase
Pin C B–
Pin D B+
Pin E D+
Pin F F+
Figure 6 – Alternator-to-Regulator Harness Plug
TG13G
Page 5
Section D: A2-214 Advanced Troubleshooting
A2-214 Regulator
DESCRIPTION AND OPERATION
A2-214 regulator is either attached directly to the outside
of alternator or remote-mounted.
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 page 8.
REMOTE-MOUNTED REGULATORS: CHECK
CONDITION OF FUSE IN WIRING HARNESS
BEFORE TROUBLESHOOTING
Page 6
TG13G
Section D: A2-214 Advanced Troubleshooting (CONT’D)
Chart 2 – No Alternator Output – Quick Diagnostic
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
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
Alternator is defective.
With DMM on resistance scale, ensure that the field resistance measured between pins F and A in
harness plug is about 1.2 (±0.2) ohms.
Yes
Alternator is defective.
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 8.
No
No
No
No
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
TG13G
Page 7
Section D: A2-214 Advanced Troubleshooting (CONT’D)
Chart 3 – No Alternator Output – Test Charging Circuit
STATIC TEST – ENGINE OFF, BATTERY SWITCH ON, KEY ON
Test for battery voltage at alternator B+ terminal. Does battery voltage exist?
Yes No
With engine running: Test for battery voltage at
regulator IGN terminal. Does battery voltage exist?
Yes
No
Repair vehicle wiring as necessary.
Continue test.
Repair vehicle wiring as necessary.
Re-test.
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. Disconnect B+ battery cable from alternator. 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. Set DMM to Diode Test. Connect red
lead to pin B in harness plug. Connect black lead to B+ terminal on alternator. Does continuity exist?
Yes
No
C625 Alternator: Alternator is defective.
C653 Alternator: Proceed to Chart 4, page 9.
With DMM on resistance scale, ensure that the field resistance measured between pins F and A in
harness plug is about 1.2 (±0.2) ohms.
Yes
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.
Alternator is defective.
No
Page 8
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 8 – Alternator-to-Regulator Harness Plug
TG13G
Section D: A2-214 Advanced Troubleshooting (CONT’D)
USE THIS DIODE
Chart 4 – Continuation of Chart 3 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 IGN terminal.
Vehicle charging circuit test is complete.
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?
Yes
Alternator is
defective.
No
No
Thermal switch
in control unit
is defective.
Figure 9 – Diode Arrangement inside C653 Drive End Housing
TG13G
Page 9
Section E: C653 w/A2-338 Advanced Troubleshooting
A2-338 Regulator
Description and Operation
A2-338 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 3 for diagnostic features and LED explanations.
This regulator has OVCO (overvoltage cutout) that will
trip at vehicle electrical system voltage above 33 volts
that exists longer than 3 seconds. OVCO feature detects
high voltage and reacts by signaling field circuit to open.
This turns off alternator (LED is f lashing RED). OVCO
circuit is reset when engine is restarted or when system
voltage drops below 26.5 V.
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.
TABLE 3 – A2-338 Regulator Diagnostics
LED COLOR STATUS
GREEN Solid
Flashing
Alternator and regulator operating normally.
Regulator is in soft start mode.
Trou b le sh o ot ing
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 field circuit, try
third restart. If OVCO circuit repeats cutout, go to Chart
5, page 11.
ACTION
No action required.
Wait 10 seconds until a lternator achieves full
rotation.
AMBER Solid
Flashing
RED Solid
Flashing
Low system volta ge — Electrical load exceeds
alternator rating at present rotor speed.
Alternator fault — No output.
High system voltage – May occur during
normal load switching.
OVCO tripped.
When loads decrease or speed increases, LED
should be solid GREEN. If not, check drive belt
and charging system connections.
Replace alternator.
If solid more than 3 seconds, OVCO will trip,
disabling charging system. LED will f lash RED.
Overvoltage condition. Attempt reset. System
diagnosis required. Go to Chart 5, page 11.
Page 10
TG13G
Section E: C653 w/A2-338 Advanced Troubleshooting (CONT’D)
Chart 5 – 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
CAUTION
Unplug alternator-to-regulator harness. Connect
DMM across pin D and pin C in harness plug.
Does battery voltage exist?
Yes
When conducting this step,
ensure that the probes do not
touch other pins, as an arc
may damage the wiring in the
harness.
No
Alternator is defective.
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.
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
Alternator is defective.
Regulator is defective.
Yes
No
Remove jumper from D+ to B+.
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
Alternator is defective.
Regulator is defective.
PIN CONNECTIONS
Pin A F–
Pin B Phase
Pin C B–
Pin D B+
Pin E D+
Pin F F+
Figure 10 – Alternator-to-Regulator Harness Plug
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: 800.643.4633 USA and Canada • TEL: 847.866.6030 outside USA and Canada • FAX: 847.492.1242
E-mail us at service@CENiehoff.com
TG13G
Page 11
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