C.E. Niehoff & Co. C703, C703A, C706 Troubleshooting Guides
C703/C703A and C706 Alternators
C.E. Niehoff & Co.
Before troubleshooting any CEN products, the service technician should:
WARNING
• read, understand, and agree to follow all information contained in this troubleshooting guide.
• understand the operational characteristics of the electrical charging system components to be tested.
• be profi cient at the use of tools and test equipment used in troubleshooting CEN products.
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 hazard(s) that
WARNING
can cause severe personal injury,
death, or substantial property
damage if ignored.
Indicates presence of hazards that
CAUTION
will or can cause minor personal
injury or property damage.
Table of Contents
Section A: Description and Operation ....................... 2-3
Section B: Schematic Diagram .................................... 4
Section C: On-Vehicle Troubleshooting ..................... 5-7
Tools and Equipment
• Digital Multimeter (DMM)
• Ammeter (digital, inductive)
• Jumper wires
• CEN 6-pin Inline Harness Test Tool A10-114
Figure 1—CEN 6-pin Inline Harness Test Tool A10-114
Testing Guidelines
Professional service technicians rely on the following
guidelines when testing electrical components.
Voltage testing:
• Set meter to proper scale and type (AC or DC).
• Be sure to zero the meter scale or identify the meter
burden by touching meter leads together. Meter burden must be subtracted from final reading obtained.
• Be sure the meter leads touch source area only.
Prevent short circuit damage to test leads or source
by not allowing meter leads to touch other pins or
exposed wires in test area.
• Be sure to use CEN tools designed especially for
troubleshooting CEN alternators when available.
See page 1 for more information.
Resistance (ohm) testing:
• Set meter to proper scale.
• Be sure to zero the meter scale or identify the meter
burden by touching meter leads together. Meter burden must be subtracted from final reading obtained.
• Be sure the meter leads touch source area only.
Prevent altering the reading by not allowing fingers
or body parts to touch meter leads or source during
reading.
• Be sure reading is taken when source is at 70ºF.
Readings taken at higher temperatures will increase
the reading. Conversely, readings taken at lower
temperatures will decrease the reading.
• Be sure to test directly at the source. Testing through
extended harnesses or cable extensions may increase
the reading.
Voltage drop testing:
• Measure voltage between B+ on alternator or source
and B- (ground) on alternator or source. Record
obtained reading. Move to batteries or other source
and measure again between B+ and B- terminals on
battery or other source. Difference between the two
readings represents voltage lost within the circuit
due to but not limited to inadequate cable gage or
faulty connections.
• Voltage drop measurements must be taken with
all electrical loads or source operating.
Dynamic/Live testing:
Definition: Connecting power and ground to a
component to test operation/function out of circuit.
1. Be sure to connect jumper leads directly and securely
to source contacts of the component being tested.
2. Be sure to make any connection to power and ground
at the power supply or battery source terminals. Do
not make connection at component source terminals
as that may create an arc and damage component
source terminals.
TG31K
Page 1
Section A: Description/Operation
CEN C703/C703A and C706 Alternators/Regulators Description and Operation
C703/C703A 28 V (350 A) and C706 28 V (300 A) alternators are internally rectified. All windings and currenttransmitting components are non-moving, so there are no brushes or slip rings to wear out.
These alternators are externally energized when the battery master switch on the vehicle is turned on and provides
power to the regulators through the IGN circuit (the A2-341 regulator can also operate without vehicle connection to
IGN, and instead provide power by sensing rotation through the regulator’s AC circuit).
Field coil is then energized. AC is rectified into DC output through diodes in drive end rectifier housing and supplied
to the battery from the alternator B+ terminal. See schematic diagram on page 4. Alternator output current is selflimiting and will not exceed rated capacity of alternator. Regulator maintains alternator output voltage at pre-determined
regulated setting (see Table 1 or 2 below for setpoints) as vehicle electrical loads are switched on and off.
Battery type selection and battery maintenance/function are the sole responsibilities of the customer.
A2-214 and A2-325 regulators furnished with some units include:
• External IGN terminal for energize connection.
• P terminal that can provide optional AC voltage tap. P terminal signal frequency (Hz) x 10 = alternator shaft rpm.
• D+ terminal that can provide DC voltage signal to vehicle electrical system, confirming alternator operation.
• Overvoltage cutout (OVCO) function. See page 5.
• (A2-214 only) Green-lensed LED. See page 5.
• (A2-325 only) Tricolored LED. See page 5.
• Regulator fixed (flat temperature compensation) setpoints shown in Table 1 are selected based on battery type.
Table 1 — A2-214 & A2-325 Regulator Setpoint Switch Position
Voltage Setpoints (±0.2 V) Battery Type
Position 1 27.5 V Maintenance
Position 2 28.0 V Maintenance
Position 3 28.5 V Maintenance-free
Position 4 29.0 V Maintenance-free
Note on Group 31 batteries: If boiling or excessive gassing occurs with high voltage
setpoint (position 3), change to medium voltage setpoint (position 2).
Figure 2—Voltage Setpoints
A2-341 regulator furnished with some units includes:
• External IGN terminal that can provide optional external energize connection. This regulator can function with or
without vehicle ignition. When necessary, regulator IGN terminal can be connected to vehicle ignition source to provide
battery voltage when engine is running. Circuit should be off (no voltage present) when vehicle ignition is off or engine
is not running.
• P terminal that can provide optional AC voltage tap. P terminal signal frequency (Hz) x 10 = alternator shaft rpm.
• D+ terminal that can provide DC voltage signal to vehicle electrical system, confirming alternator operation.
• Overvoltage cutout (OVCO). See page 6.
• Tricolored LED. See page 6.
• Temperature-voltage sense/J1939 harness connector that can be used with optional harness.
— When optional temperature-voltage sense/J1939 harness is not connected, regulator will operate in fixed voltage
setting determined by the select switch position on the bottom of the regulator. See Column 2 in Table 2.
— When optional temperature-voltage sense/J1939 harness is connected, regulator will automatically optimize the
charge voltage for battery type based on temperature. Also, vehicle manufacturer-requested functions of J1939
interface are available through connector. See Column 3 in Table 2.
Table 2 — A2-341 Regulator Voltage/Battery Switch Position
Switch Position
Page 2
T-VS/J1939 Harness Not
Connected (Voltage Select)
Position 1 27.5 V Maintenance (D Category)
Position 2 28.0 V Maintenance-free (Group 31)
Position 3 28.5 V AGM
Position 4 29.0 V
T-VS/J1939 Harness Connected
(Battery Select)
DO NOT USE POSITION # 4
Figure 3—Voltage/Battery Switch
TG31K
Section A: Description and Operation (CONT’D)
B+ terminal on
back side of
control housing
B– terminal
C703 ADE View
IGN terminal
D+ terminal
B+ bolt
terminal
Figure 4 — C703/C703A Alternator Terminals
(Regulator Attached to Alternator)
C703A ADE View
P terminal
B– terminal
stud
C706 ADE View
P terminal
Figure 5 — C706 Alternator Terminals
(Regulator Attached to Alternator)
D+ terminal
IGN terminal
TG31K
Page 3
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