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Caution – C.E. Niehoff & Co. N1240-3/N1243-2 Troubleshooting Guides User Manual

Page 4

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Page 4

TG0040A

Section 3: Basic Troubleshooting

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.

A. Tools and Equipment for Job

Digital Multimeter (DMM)

Ammeter (digital, inductive)

Jumper wires

B. Identification Record

List the following for proper troubleshooting:

Alternator model number ____________________

Regulator model number _____________________

CAUTION

SYMPTOM

ACTION

TABLE 4 – System Conditions

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.

Check: defective alternator

and/or regulator.

Check: defective regulator.
Check: alternator.
Check: presence of energize

signal to E terminal on
regulator.

Check: battery voltage at alter-

nator output terminal.

Check: defective alternator

and/or regulator.

Low Voltage Output

High Voltage Output

No Voltage Output

TROUBLESHOOTING
Shut down vehicle and restart engine. If alternator
functions normally after restart, a “no output condi-
tion” was normal response of voltage regulator to
overvoltage condition. Inspect condition of electrical
system.
If you have reset alternator once, and electrical
system returns to normal charge voltage condition,
there may have been a one time, overvoltage spike
that caused 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 a third
time, go to Chart 1, page 5.

C. Preliminary Check-out

Check symptoms in Table 4 and correct as necessary.

4.

Connect meters to alternator

Connect red lead of DMM to alternator B+
terminal and black lead to alternator B–
terminal. Clamp inductive ammeter on B+
cable.

5.

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
excessive voltage. Go to
Table 4 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

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 5.