C702D 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
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.
TG65A
Page 1
Section A: Wiring Diagram
CEN C702D Alternator
Description and Operation
C702D 28 V, 350 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. Field coil is then energized. Regulator
maintains alternator output voltage at regulated
setting as vehicle electrical loads are switched on
and off. Alternator output current is self-limiting
and will not exceed rated capacity of alternator.
A2-332 regulator furnished with most units
has D+ terminal that can provide signal to
vehicle electrical system, confirming alternator
operation. Regulator also has a P terminal that
can provide an optional AC voltage tap.
Regulator also provides overvoltage
cutout (OVCO). Regulator also has a
tri-color LED (see page 4).
B+ Terminal
P Terminal
LED
B– Terminal
(either side)
Figure 1 — C702D
D+ Terminal
IGN Terminal
Page 2
Figure 2 — C702D Alternator with Regulator
TG65A
Section B: Basic Troubleshooting
Tools and Equipment for Job
• Digital Multimeter (DMM)
• Ammeter (digital, inductive)
• Jumper wire
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
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
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. Check IGN, D+, and P terminal
w iring f rom regu lator to vehicle components. Check
ignition switch for proper operation. 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 a lternator B+ termin al
and black lead to alternator B– terminal. Clamp
inductive ammeter on B+ cable.
6. Operate vehicle
Observe charge voltage.
If charge voltage is above
33 volts, 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.
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
shou ld decrease. I f charge voltage does not incre ase
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 1, page 5.
CAUTION
TG65A
Page 3
Section C: Advanced Troubleshooting
A2-332 Regulator
Description and Operation
A2-332 regulator is attached directly to the outside of
alternator.
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.
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 flashing RED). OVCO
circuit is reset when engine is restarted.
TABLE 2 – A2-332 Regulator Diagnostics
LED COLOR STATUS
GREEN Solid
AMBER Solid
Flashing
RED Solid
Flashing
Alternator and regulator operating normally.
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.
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 field circuit, try
third restart. If OVCO circuit repeats cutout, go to Chart
1, page 5.
ACTION
No action required.
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 w ill f lash RED.
Overvoltage condition. Attempt reset. System
diagnosis required. Go to Chart 1, page 5.
Page 4
TG65A
Section C: Advanced Troubleshooting (CONT’D)
Chart 1 – No A lternator Output
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
With key off, engine off: 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.
No
Yes
No
Alternator is defective.
With DMM on resistance scale, ensure that the field resistance measured between pins F and C in
harness plug is about 1.3 (±0.2) ohms.
Yes
No
Alternator is defective.
Install a jumper from pin F in harness plug to B+ terminal on alternator. Touch shaft with steel tool to
detect significant magnetism. Is shaft magnetized?
Yes
No
Alternator is defective.
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
Alternator is
defective.
Thermal switch
in control unit
is defective.
No
CONNECTIONS
A B+ Sense
B AC IN 2
C B–
D B+
E AC IN 1
F F+
Figure 3 – Alternator-to-Regulator Harness Plug
If you have quest ions about your alternator or any of these test procedures, or if you need to locate a Factory Authori zed Serv ice 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
TG65A
Page 5
Loading...