600 Series Troubleshooting Guide
for C651 and C654 Alternators
Hazard Definitions
These terms are used to bring attention to presence of hazards
of various risk levels or to important information concerning
product life.
CAUTION
personal injury or property damage if ignored.
NOTICE
maintenance that are important but not related to
personal injury hazards.
Indicates presence of hazards
that will or can cause minor
Indicates special instructions
on installation, operation or
Table of Contents
Section 1: Wiring Diagram ....................................... 2
Section 2: Basic Troubleshooting ............................ 3
Section 3: Advanced Troubleshooting ................. 4 – 7
Battery Conditions
NOTICE
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 charac-
teristics 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.
Until temperatures of electrical
system components stabilize, these
Charge Volt and Amp Values
The volt and amp levels are a function of the batterystate 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 and 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 charge amps rates.
• 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 charge amp rates.
• Battery Voltage: Steady-state voltage value as
measured 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 mea-
suring voltage at battery positive terminal or
alternator B+ terminal.
• Surface Charge: A higher than normal battery
voltage 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.
TG0010C
Page 1
Section 1: Wiring Diagram
CEN C651 and C654 Alternators
Description and Operation
C651 28 V (240 A)/14 V (100 A) and C654 28 V
(260 A) /14 V (100 A) alternators are internally
rectified. All windings and current-transmitting
components are non-moving, so there are no
brushes or slip rings to wear out. Energize
switch activates regulator. Regulator cycles
field coil off and on until system voltage is
is reached. Upper voltage (28 V) is rectified
with standard diodes. Lower voltage (14 V)
circuit output current is controlled by
SCRs in the drive end housing. Alternator
output current is self-limiting and will
not exceed rated capacity of alternator.
A2-306 regulator used with these units:
• is for use with batteries connected in
series, not parallel.
CAUTION
series not parallel circuits. See Figures 2 and 3 for connections.
• maintains alternator output voltage at regulated
setting as vehicle electrical loads are switched
on and off.
Regulator is designed to
control system through
TT
T
TT
R Terminal
TT
T
TT
TT
T
TT
TT
T
TT
E Terminal
Tricolor (R, A, G) diagnostic LED
28 V B+ Terminal
14 V B+ Terminal
B– Terminal
TT
T
TT
TT
T
TT
TT
T
TT
• monitors low and high batteries in system separately.
• limits 14 V alternator output current to 100 A. 14 V
source from R terminal on regulator is limited to 1 A
when alternator is rotating.
STATOR
RECTIFIER
SCR GATE
STATOR
FIELD
Figure 1 — C651 and C654 Alternator Terminals
28 V
B+
14 V
ENERGIZE
SWITCH
A
B
C
D
E
F
G
H (unused)
E
REGULATOR
14 V LOAD
28 V LOAD
R
BATTERY
BATTERY
Page 2
B–
REGULATOR RECEPTACLE
ALTERNATOR
Figure 2 — C651 and C654 Alternator with Regulator
TG0010C
Section 2: Basic Troubleshooting
A . Tools and Equipment for Job
• Digital Multimeter (DMM)
• Ammeter (digital, inductive)
• Jumper wire
B. Identification Record
List the following for proper troubleshooting:
Alternator model number _______________________
❏
Regulator model number _______________________
❏
Setpoints listed on regulator ____________________
❏
C. 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
No 14 V 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 and/
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 and/
or regulator.
Check:defective regulator.
Go to Chart 3, page 6.
ACTION
D. Basic Troubleshooting
1. Inspect charging system components
for damage
Check connections at B– cable, B+ cables,
and regulator harness. Repair or replace any
damaged component before troubleshooting.
2. Inspect 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 meters as shown in Figure 3, page 4.
5. Operate vehicle
Observe charge voltage.
CAUTION
battery, 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.
Regulator setpoints indicate two different voltage
measurements for this system. First setpoint
is sum of low battery and high battery voltage
measurements. Second setpoint is voltage
measured across low battery only.
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 in each circuit
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 4, page 7.
If charge voltage is above
16 V on either high or low
TG0010C
Page 3
Section 3: Advanced Troubleshooting
A2-306 Regulator
DESCRIPTION AND OPERATION
A2-306 Regulator with OVCO is attached directly
to the outside of alternator.
Main diagnostic feature of A2-306 regulator is
tricolored (red, amber, green) LED next to harness
receptacle on regulator. LED works like a voltmeter,
measuring charging voltage. See Table 2 on page 5
for diagnostic features and LED explanations.
Regulator with OVCO (overvoltage cutout) will trip
at one of the following conditions:
• Voltage higher than regulator setpoint that exists
longer than 3 seconds at low battery. OVCO
feature detects high voltage and reacts by signaling relay in F+ alternator circuit to open. This
turns off alternator (LED is steady AMBER light).
Restarting engine resets OVCO circuit. Regulator
regains control of alternator output voltage.
• Voltage lower than regulator setpoint that exists
longer than 3 seconds at low battery. OVCO
feature detects low voltage and reacts by signaling
relay in F+ alternator circuit to open. This turns
off alternator (LED is steady RED light). Restarting
engine resets OVCO circuit. Regulator regains
control of alternator output voltage.
• Voltage higher than regulator setpoint that exists
longer than 3 seconds at high battery. OVCO
feature detects high voltage and reacts by signaling relay in F+ alternator circuit to open. This
turns off alternator (LED is steady RED light).
Restarting engine resets OVCO circuit. Regulator
regains control of alternator output voltage.
TROUBLESHOOTING
Before troubleshooting, make sure batteries are
connected in series, not parallel circuits. See Figures
2 and 3 for connections.
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 a third
time, check color of LED while engine is running.
AMBER LED - go to Chart 1, page 5.
RED LED - go to Chart 2, page 5.
Listed regulator setpoints:
Position #1 - 27.5 V
Position #2 - 28.0 V ± 0.2 V/14.0 V ± 0.1 V
Position #3 - 28.5 V ± 0.2 V/14.2 V ± 0.1 V
Position #4 - 29.0 V ± 0.2 V/14.5 V ± 0.1 V
NOTICE
control voltage. Regulator measures A to B and B to C
separately.
± 0.2 V/13.8 V ± 0.1 V
Measurement from A to C
is not used by regulator to
C
Page 4
Meter placement for
high battery reading
B
Meter placement for
low battery reading
A
Figure 3 – Meter Placement
TG0010C
Section 3: Advanced Troubleshooting
TABLE 2 – A2-306 Regulator Diagnostics
(CONT’D)
LED COLOR STATUS
(key on, engine running)
AMBER Steady
(key on, engine off)
Flashing
RED Steady
(key on, engine off)
Flashing
GREEN/
AMBER
Flashing both
colors
Chart 1 – AMBER LED On Steady – No Alternator Output – Test OVCO Circuit
ACTION
Alternator and regulator operating normally.GREEN Flashing
Low battery tripped OVCO.
Alternator not rotating or 14 V output
voltage unstable.
High or low battery tripped OVCO.
28 V output voltage unstable.
Low battery amp draw exceeds 125 amps.
No action required.
See Chart 1 below.
See Chart 2 below.
1. Check battery, system cable connections
and grounds.
2. Perform load analysis.
3. If OK, replace alternator.
Make sure batteries are properly charged before proceeding.
Replace regulator with known good regulator. Run engine. Does OVCO trip?
Yes
TT
T
TT
Alternator is defective.
Chart 2 – RED LED On Steady – No Alternator Output – Test OVCO Circuit
Make sure batteries are properly charged before proceeding.
With engine running, measure voltage at low battery B+ terminal. See ➀ in Figure 3 on page 4.
Is voltage equal to regulator set point or no more than 1 V below set point?
Yes
TT
T
TT
Replace existing regulator with known good regulator. Run engine.
Does OVCO trip?
Yes
TT
T
Alternator is defective.
TT
Original regulator is defective.
No
TT
T
TT
No
TT
T
TT
Original regulator is defective.
No
TT
T
TT
System is overloaded. Check for
excessive draw from
accessories.
TG0010C
Page 5
Section 3: Advanced Troubleshooting
(CONT’D)
Chart 3 – No 14 V Alternator Output – Test Circuit
With engine off, is battery voltage present at alternator 14 V B+ terminal?
Yes
TT
T
TT
Connect DMM red lead to pin E on alternator-to-regulator harness plug. Connect black
lead to pin C on same plug. Does battery voltage exist?
Yes
TT
T
TT
Substitute a known good regulator. Run engine. Is regulator
setpoint voltage present?
Yes
No
TT
T
TT
Repair vehicle wiring as necessary.
Continue test.
TT
T
TT
No
TT
T
Alternator is defective.
TT
No
TT
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TT
Original regulator
was defective.
PIN CONNECTIONS
Figure 4 – Alternator-to-Regulator Harness Plug
Pin A F–
Pin B SCR Gate
Pin C B–
Pin D 28 V B+
Pin E 14V B+
Pin F F+
Pin G AC Signal
Pin H Not Used
TT
T
TT
Alternator is
defective.
Page 6
TG0010C
Section 3: Advanced Troubleshooting
Chart 4 – No Alternator Output – Test Charging Circuit
STATIC TEST – ENGINE OFF, BATTERY SWITCH ON, KEY ON
Test for battery voltage at both alternator 28 V and 14 V B+ terminals. Does
battery voltage exist at both terminals?
Yes
Repair vehicle wiring as necessary. Continue test.
TT
T
TT
Jumper 28 V B+ terminal on alternator to E terminal on regulator. Run engine. Does alternator charge?
Yes
TT
T
TT
Turn off engine, leave key on. Remove jumper wire. Go to
E terminal on regulator. Test for battery voltage going into
E terminal from battery. Does battery voltage exist?
Yes
Repair vehicle circuit to E terminal.
Vehicle charging circuit test is
complete.
TT
T
Run engine and re-test charging circuit for operation.
TT
No
TT
T
TT
TT
T
TT
Turn off engine, leave key on. Connect jumper
wire from pin F in harness plug to 28 V B+
terminal on alternator. Does spark occur?
Alternator is
defective.
With previous jumper still in place, connect
another jumper wire from pin A in harness plug
to B– terminal on alternator. Spark will occur.
Touch steel tool to shaft to detect significant
magnetism. Is shaft magnetized?
Yes
TT
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TT
Yes
No
TT
T
TT
TT
T
TT
No
TT
T
TT
No
TT
T
TT
No
PIN CONNECTIONS
Figure 5 – Alternator-to-Regulator Harness Plug
Pin A F–
Pin B SCR Gate
Pin C B–
Pin D 28 V B+
Pin E 14V B+
Pin F F+
Pin G AC Signal
Pin H Not Used
TT
T
TT
Alternator is defective.
TT
T
TT
Disconnect jumper wires. Connect DMM red
lead to pin D in alternator-to-regulator harness
plug. Connect black lead to pin C in same plug.
Does 24 V battery voltage exist?
Yes
Alternator is defective.
TT
T
TT
Connect DMM red lead to pin E in alternatorto-regulator harness plug. Connect black lead
to pin C in same plug. Does 12 V battery voltage
exist?
Yes
TT
T
TT
Regulator is
defective.
No
TT
T
TT
No
TT
T
TT
Alternator is
defective.
TG0010C
Page 7
Notes
If you have questions about your alternator or any of these test procedures, or if you need to locate a Factory Authorized Service Distributor, please contact us at:
TEL: 800.643.4633 USA and Canada • TEL: 847.866.6030 outside USA and Canada • FAX: 847.492.1242
Page 8
C. E. Niehoff & Co.• 2021 Lee Street • Evanston, IL 60202 USA
E-mail us at support@ceniehoff.com
TG0010C
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