C.E. Niehoff & Co. C633 Installation
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
C633 Alternator
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
Section B: Schematic Diagram .................................... 3
Section C: On-Vehicle OVCO Troubleshooting .............. 4
Section D: On-Vehicle 28 V No Output
Troubleshooting .......... 5
Section E: On-Vehicle 14 V No Output
Troubleshooting .......... 6
Tools and Equipment
• Digital Multimeter (DMM)
• Ammeter (digital, inductive)
• Jumper wires
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.
TG80A
Page 1
Section A: Description/Operation
CEN C633 Alternator/Regulator Description and Operation
C633 28 V 220 A alternator with optional 28 V/14 V (50 A maximum on 14 V) is internally rectified. All windings and
current-transmitting components are non-moving, so there are no brushes or slip rings to wear out.
This alternator is externally energized when the battery master switch on the vehicle is turned on and provides power
to the regulator through the IGN circuit. Regulator monitors alternator rotation and provides field current only when it
detects alternator shaft rotating at suitable speed.
After regulator detects alternator rotation, it gradually applies field current (soft start), preventing an abrupt mechanical
load on accessory drive system. The soft start may take up to 10 seconds at full electrical load. 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 3. Alternator output current is self-limiting and will not exceed rated capacity of alternator.
The regulator maintains alternator output voltage at regulated settings (see below) as vehicle electrical loads are
switched on and off.
Battery type selection and battery maintenance/function are the sole responsibilities of the customer.
A2-355 regulators furnished with some units include:
• External IGN terminal for energize connection.
• AC terminal for optional AC voltage tap. AC terminal signal frequency (Hz) x 10 = alternator shaft rpm.
• Optional single or dual voltage operation.
—Allows single-voltage (28 V only). 14 V is not available as a single-voltage application with this regulator.
—Allows optional 28 V/14 V dual voltage operation only from this regulator when phase cable from alternator is
connected to regulator and 14 V cabling from vehicle is attached to regulator 14 V terminal.
• Overvoltage cutout (OVCO) function. This regulator has OVCO (overvoltage cutout) that will trip at vehicle electrical
system voltage above 32 volts in a 28 V system or 16 V in a 14 V system that exists longer than 2 seconds. OVCO
feature detects high voltage and reacts by signaling relay in alternator field circuit to open. This turns off alternator.
OVCO circuit is reset when engine is restarted.
• Regulator has negative temperature compensation. Setpoints are 28.0± 0.2 V and 14.0 ± 0.2 V at 75°F.
IGN terminal
B– terminal
AC terminal
28 V B+
terminal
14 V B+
terminal
Figure 1 — C633 Alternator and A2-355 Regulator Terminals
AC
14 V
IGN
Page 2
TG80A
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