Cen N1225 User manual

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N1225 / N1237 / N1505 Alternators
Troubleshooting Guide
C.E. Niehoff & Co.
Page 1TG17C
CONTENTS
Section 1: Wiring ................................................................2
Section 2: Basic Troubleshooting.....................................3
Section 3: Advanced Troubleshooting .............................4
Battery Charging Conditions
The following conditions may be observed during cold-
start voltage tests until temperatures of electrical system
components stabilize. The time it takes to reach optimum
voltage and amps will vary with engine speed, load, and
ambient temperature.
Maintenance/Low Maintenance Lead-Acid Battery:
Traditional lead acid batteries require lowest charge volt-
age of all vehicle battery chemistries. Battery cells must
be maintained by periodically topping off with distilled
water as required.
Maintenance-free Lead-Acid Battery:
Maintenance-free batteries are similar to Maintenance/
Low Maintenance batteries, but may require slightly higher
charge voltage.
Deep-cycle/Marine Maintenance-free Battery:
Charge acceptance of these batteries may display charac-
teristics similar to maintenance-free batteries and may
charge faster due to generally lower capacity relative to
size.
AGM (Absorbed Glass Mat) Maintenance-free Battery:
These dry-cell batteries respond better than standard
maintenance-free batteries. If battery state of charge
(SOC) drops to 75% or less, batteries should be
recharged to 95% or higher separately from engine charg-
ing system to avoid damaging charging system
components and to provide best overall performance.
Charge acceptance of these batteries may display charac-
teristics similar to maintenance batteries, but may require
higher charge voltage and will draw signicant current (<100
amps) when under 50% SOC.
Lithium Battery:
Lithium batteries have unique charging characteristics that
differ from lead acid. These batteries require charging
systems congured specically for lithium battery chemis-
tries. Contact CEN for more information on lithium battery
charging systems and 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 nal 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 trou-
bleshooting CEN alternators when available.
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 nal reading obtained.
• Be sure meter leads touch source area only. Allowing
ngers or body parts to touch meter leads or source
during reading may alter reading.
• Be sure reading is taken when source is at 70ºF. Read-
ings taken at higher temperatures will increase the
reading. Conversely, readings taken at lower tempera-
tures will decrease the reading.
• Be sure to test directly at the source. Testing through
extended harnesses or cable extensions may increase
the reading.
• "OL" as referenced in this document refers to open cir-
cuit: "innite" resistance, typically in very high kilo- or
megaohm range depending on meter and settings.
Diode testing:
• Diodes allow current to ow in one direction only. Typi-
cal voltage drop in forward bias can range from 0.1-
0.85V. Meter should read OL in reverse bias. Check
meter user manual for meter-specic testing guidelines.
Voltage drop testing:
• Measure voltage between B+ on alternator or power
source and B- (ground) on alternator or source. Record
reading. Move to batteries or other power source and
measure again between B+ and B- terminals on battery
or other power source. The difference between the two
readings represents voltage lost within circuit due to,
but not limited to, inadequate cable gauge or faulty con-
nections.
• Voltage drop measurements must be taken with all elec-
trical loads or source operating.
Dynamic/Live testing (Connecting power and ground to
component to test operation/function out of circuit):
• Connect jumper leads directly and securely to power
source contacts of component being tested.
• Make any connection to power and ground at power
supply or battery source terminals. Do not make con-
nection at component source terminals, as that may
create an arc and damage component source terminals.
Testing Guidelines
Professional service technicians rely on the following
guidelines when testing electrical components.

Page 2 TG0017B
Section 1: Wiring Diagram
CEN N1505-1, N1237-1, and N1225-1
Dual Voltage Alternators Description
and Operation
N1505-1 28 V 100 A and N1237-1/N1225-1 28 V
200 A alternators all with optional 28 V/14 V (50 A
maximum on 14 V) are internally rectified. All wind-
ings and current-transmitting components are non-
moving, so there are no brushes or slip rings to wear
out.
After engine is running, N3135 regulator receives
energize signal. Regulator monitors alternator rotation
and provides field current only when it detects alerna-
tor shaft rotating at suitable speed.
After regulator detects alternator rotation, it gradually
applies field current, preventing an abrupt mechani-
cal load on accessory drive system. The soft start may
take up to 10 seconds at full electrical load.
N3135 regulator used with these units also
• is negative temperature compensated. Setpoints
are 28.0 ± 0.2 V and 14.0 ± 0.2 V at 75° F.
• provides overvoltage cutout (OVCO). Regulator will
trip OVCO when system voltage rises above 32 V
in a 28 V system (16 V in a 14 V system) for longer
than 2 seconds. OVCO feature detects high volt-
age and reacts by signaling relay in F– alternator
circuit to open, turning off alternator. Restarting
engine resets OVCO circuit.
• maintains alternator output voltage at regulated
settings as vehicle electrical loads are switched
on and off.
B– terminal
Figure 2 — N1505-1/N1237-1/N1225-1 Alternators with N3135 Regulator Wiring Diagram
Figure 1 — N1505-1/N1237-1/N1225-1 Alternators and
N3135 Regulator Terminals
14 V B+
terminal
28 V B+
terminal



14 V
AC
IGN
AC terminal

IGN terminal

• can be used in single or dual voltage with these
alternators.
— Allows single-voltage operation (28 V only).
14 V is not available as a single voltage appli-
cation with this regulator.
— Provides optional 28 V/14 V output only from
the regulator when phase cable from alterna-
tor is connected to regulator.
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Section 1: Wiring Diagram
Page 2 TG17C

Page 3
TG0017B
D . Basic Troubleshooting
1. Inspect charging system components
Check connections at ground cables, positive
cables, and regulator harness. Repair or replace
any damaged component before troubleshooting.
2. Inspect connections of vehicle batteries
Connections must be clean and tight.
3. Determine battery type, voltage and state
of charge
Batteries must be all the same type for system
operation. If batteries are discharged, recharge
or replace batteries as necessary. Electrical
system cannot be properly tested unless batter-
ies are charged 95% or higher. See page 1 for
details. Nominal battery voltage for 28 V systems
is 25.2 ± 0.2 V; for 14 V systems is 12.6 ± 0.2 V.
SYMPTOM ACTION
TABLE 1 – System Conditions
Check: loose drive belt; low bat-
tery state of charge.
Check: current load on system
is greater than alternator
can produce.
Check: defective alternator
and/or regulator.
Check: wrong regulator.
Check: defective regulator.
Check: alternator.
Check: presence of energize
signal.
Check: battery voltage at alterna-
tor output terminal.
Check: defective alternator
and/or regulator.
Go to Chart 2, page 5.
Low Voltage Output
High Voltage Output
No 28 V Output
C. Preliminary Check-out
Check symptoms in Table 1 and correct if necessary.
A. Tools and Equipment for Job
• Digital Multimeter (DMM)
• Ammeter (digital, inductive)
• Jumper wires
B. Identication Record
List the following for proper troubleshooting:
Alternator model number ______________________
Regulator model number ______________________
Setpoint listed on regulator _____________________



Section 2: Basic Troubleshooting
No 14 V Output
CAUTION
Less than 25 V or 12.4 V indicates no charge
condition when engine is running.
4. Connect meters to alternator
Connect red lead of DMM to alternator 28 V B+
terminal and black lead to alternator B– termi-
nal. Clamp inductive ammeter on 28 V B+
cable.
5. Operate vehicle
Observe charge voltage at batteries with engine
running (nom. 27-28 V or 13.5-14.0 V).
If charge voltage is above
32 V for 28 V system or
16 V for 14 V system,
immediately shut down
system. Electrical system
damage may occur if charg-
ing system is allowed to
operate at excessive volt-
age. 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.
6. Observe charge volts and amps in each circuit
Charge voltage should increase and charge amps
should decrease. If charge voltage does not in-
crease 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 1, page 4.
9. Check OVCO (overvoltage cutout) circuit.
Shut down vehicle and restart engine. If
alternator functions normally after restart, a
“no output condition” was normal response of
voltage regulator to overvoltage condition.
Inspect condition of electrical system, includ-
ing loose battery cables, both positive and
negative. If battery disconnects from system, it
could cause overvoltage condition in electrical
system, causing OVCO circuit to trip.
If you have reset alternator once, and electrical
system returns to normal charge voltage condi-
tion, there may have been a one time, overvolt-
age spike that caused 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 Chart 3, page 6.
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Section 2: Basic Troubleshooting
Page 3TG17C

Page 4 TG0017B
Section 3: Advanced Troubleshooting
Shut off engine. With key off, engine off: Test for battery voltage at alternator 28 V B+
terminal. Does battery voltage exist?
Yes No
Repair vehicle ignition circuit wiring as necessary. Continue test.
Chart 1 – No 28V Alternator Output – Test Charging Circuit
With DMM, check resistance across field coil. Connect red lead of DMM to socket A in alternator-to-regulator
harness plug. Connect black lead to B+ terminal on alternator. Does meter show 1.8 to 2.2 ohms?
Yes No
STATIC TEST – KEY ON, ENGINE OFF


Yes
Test phase signal into regulator (AC). Set meter to diode tester:
Connect red lead of DMM to socket C of regulator harness and
black lead to socket B. Meter should show voltage drop value.
Then reverse meter lead connections. Meter should show OL
(blocking).
No


Shut down vehicle and restart engine. Does alternator function normally after restart?
Yes No


Regulator responded to overvoltage condition.
Go to Chart 3 on page 6 to troubleshoot OVCO.
Figure 3 – Alternator-to-Regulator 4-Socket
Harness Plug
SOCKET CONNECTIONS
A F–
B Phase Signal AC
C B–
D 28 V B+
With key on, engine running: Test for battery voltage between IGN terminal on regulator and alternator
B– terminal. Does 28 V battery voltage exist?
Yes No


With key off, engine off: Remove alternator-to-regulator 4-pin harness from regulator. Test for battery volt-
age across sockets D and C in harness plug. Does 28 V battery voltage exist?
Alternator is defective.

Alternator is defective.

Alternator is defective.

Regulator is defective.
Yes
Connect jumper wire from socket A in regulator harness plug to B– terminal
on alternator. Spark will occur. Touch steel tool to shaft to detect significant
magnetism. Is shaft magnetized?
No


Repair vehicle ignition circuit wiring as necessary. Continue test.
Yes No

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Section 3: Advanced Troubleshooting
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Page 5
TG0017B
Section 3: Advanced Troubleshooting
(CONT’D)
Chart 2 – No 14 V Alternator Output – Test Circuit
Figure 5 – Phase Connection 3-Pin Harness Plug
PIN CONNECTIONS
A Phase P1
B Phase P2
C Phase P3
Shut off engine. With key off, engine off: Test for battery voltage of 14 V output terminal
on regulator. Does +14 V battery voltage exist?
Yes No
Repair vehicle wiring as necessary.


Yes
Set DMM to diode tester. Connect red lead of DMM
to socket C of regulator harness plug and black
lead to each phase pin in phase harness plug. Meter
should show voltage drop value.
Then reverse meter lead connections. Meter should
show OL (blocking).
No

Alternator is defective.

Regulator is defective.
Figure 4 – Alternator-to-Regulator 4-Socket Harness Plug
SOCKET CONNECTIONS
A F–
B Phase Signal AC
C B–
D 28 V B+
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Section 3: Advanced Troubleshooting (cont.)
Page 5TG17C

Page 6 TG0017B
(CONT’D)
Section 3: Advanced Troubleshooting
Yes No
Alternator is defective.
Unplug alternator-to-regulator 4-socket harness from regulator. Connect red lead from DMM to pin A in
plug. Connect black lead to pin D in plug. Does resistance read 1.8 ± 2.2 ohms?
Chart 3b – No 28 V Alternator Output – Test OVCO Circuit
Yes No
Replace existing regulator with known good regulator.
Run engine. Does OVCO trip?
Alternator is defective. Original regulator is
defective.


Chart 3a – No 14 V Alternator Output – Test OVCO Circuit
Yes No
With red lead from DMM connected to pin A in plug, connect black lead to B– terminal. Does
resistance read OL (out of limits)?
Alternator is defective.

Chart 3 – OVCO Trip – Determine 28 V or 14 V
Yes No
28 V side tripped OVCO circuit.
Go to Chart 3b.
With meter red lead on 28 V B+ at battery and black lead on chassis ground, start engine.
Watch meter dial: Does meter read charge voltage above 29 V?

14 V side tripped OVCO circuit.
Go to Chart 3a.




Figure 6 – Alternator-to-Regulator 4-Socket Harness Plug
SOCKET CONNECTIONS
A F–
B Phase Signal AC
C B–
D 28 V B+
Yes No
Original regulator
is defective.
Replace regulator with known good regulator.
Run engine. Does OVCO trip?
Alternator
is defective.


Yes No
Alternator is defective.
Unplug alternator-to-regulator 4-socket harness from regulator. At receptacle on regulator, connect red lead
from DMM to pin C. Connect black lead to B– terminal. Does resistance read OL (out of limits)?

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Section 3: Advanced Troubleshooting
Page 6 TG17C

Page 7
TG0017B
Notes
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Page 7TG17C
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:
C. E. Niehoff & Co.• 2021 Lee Street • Evanston, IL 60202 USA
TEL: [phone] USA and Canada • TEL: [phone] outside USA and Canada • FAX: [phone]
E-mail us at [e-mail]