Cen N1225 User manual

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

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.

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.

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).



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?



Repair vehicle ignition circuit wiring as necessary. Continue test.

Yes No



Section 3: Advanced Troubleshooting

Page 4 TG17C

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).



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+

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)?



Section 3: Advanced Troubleshooting

Page 6 TG17C

Page 7

TG0017B

Notes

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: 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

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