Page 1
TG0040A
Table of Contents
Section 1: Wiring ......................................................... 2
Section 2: CAN/J1939 Diagnostics .............................. 3
Section 3: Basic Troubleshooting ................................ 4
Section 4: Advanced Troubleshooting ......................... 5
Battery Conditions
Until temperatures of electrical
system components stabilize, these
conditions may be observed during
cold start voltage tests.
• Maintenance or low maintenance battery:
— Immediately after engine starts, system volts are
lower than regulator setpoint with medium amps.
— 3-5 Minutes into charge cycle, system volts are
higher and amps are dropping.
— 5-10 Minutes into charge cycle, system volts are
at, or nearly at, regulator setpoint and amps are
reduced to a minimum.
— Low maintenance battery has same characteris-
tics with slightly longer recharge times.
• Maintenance-free battery:
— Immediately after engine start, system volts
are lower than regulator setpoint with low
charging amps.
— 15-30 minutes into charge cycle, volts and amps
are still low.
— 15-30 minutes into charge cycle, volts increase
several tenths. Amps increase gradually, then
quickly, to medium to high amps.
— 20-35 minutes into charge cycle, volts increase
to setpoint and amps decrease.
• High-cycle maintenance-free battery:
— These batteries respond better than standard
maintenance-free. Charge acceptance of these
batteries may display characteristics similar to
maintenance batteries.
NOTICE
Hazard Definitions
These terms are used to bring attention to presence of hazards
of various risk levels or to important information concerning
product life.
NOTICE
N1240/N1243 Series Troubleshooting Guide
for N1240-3/N1243-2 Alternators
Charge Volt and Amp Values
The volt and amp levels are a function of the battery
state of charge. If batteries are in a state of discharge,
as after extended cranking time to start the engine, the
system volts, when measured after the engine is started
will be lower than the regulator setpoint and the system
amps will be high. This is a normal condition for the
charging system. The measured values of system volts
and amps will depend on the level of battery discharge.
In other words, the greater the battery discharge level,
the lower the system volts and higher the system amps
will be. The volt and amp readings will change, system
volts reading will increase up to regulator setpoint and
the system amps will decrease to low level (depending
on other loads) as the batteries recover and become
fully charged.
• Low Amps: A minimum or lowest charging system
amp value required to maintain battery state of
charge, obtained when testing the charging system
with a fully charged battery and no other loads
applied. This value will vary with battery type.
• Medium Amps: A system amps value which can
cause the battery temperature to rise above the
adequate charging temperature within 4-8 hours of
charge time. To prevent battery damage, the charge
amps should be reduced when battery temperature
rises. Check battery manufacturer’s recommenda-
tions for proper rates of charge amps.
• High Amps: A system amps value which can cause
the battery temperature to rise above adequate
charging temperature within 2-3 hours. To prevent
battery damage, the charge amps should be reduced
when the battery temperature rises. Check battery
manufacturer’s recommendations for proper rates
of charge amps.
• Battery Voltage: Steady-state voltage value as
measured with battery in open circuit with no
battery load. This value relates to battery state of
charge.
• Charge Voltage: A voltage value obtained when the
charging system is operating. This value will be
higher than battery voltage and must never exceed
the regulator voltage setpoint.
• B+ Voltage: A voltage value obtained when measur-
ing voltage at battery positive terminal or alternator
B+ terminal.
• Surface Charge: A higher than normal battery
voltage occurring when the battery is removed from
a battery charger. The surface charge must be
removed to determine true battery voltage and state
of charge.
• Significant Magnetism: A change in the strength or
intensity of a magnetic field present in the alternator
rotor shaft when the field coil is energized. The
magnetic field strength when the field coil is ener-
gized should feel stronger than when the field is not
energized.
• Voltage Droop or Sag: A normal condition which
occurs when the load demand on the alternator is
greater than rated alternator output at given rotor
shaft RPM.
Indicates presence of hazards that
will or can cause minor personal
injury or property damage if
ignored.
Indicates special instructions on
installation, operation or mainte-
nance that are important but not
related to personal injury hazards.
CAUTION
(10 pages)
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