User Manual

SENR9977 59
TestingandAdjustingSection
Voltage drops that are greater than the amounts
inTable10arec
aused most often by the following
conditions:
•
Loose connect
ions
•
Corroded connections
•
Faulty switch contacts
Diagnosis Pro cedure
The procedure
s for diagnosing the starting motor
are intended to help the technician determine if a
starting motor needs to be replaced or repaired. The
procedures a
re not intended to cover all possible
problems and conditions. The procedures serve only
as a guide.
Note: Do not crank the engine for more than 30
seconds. Allow the starter to cool for two minutes
before cran
king the engine again.
If the starting motor does not crank or cranks slow,
perform the
following procedure:
1. Measure the voltage of the battery.
Measure the voltage across the battery posts with
the multimeter when you are cranking the engine
or attempti
ng to crank the engine. Do not measure
the voltage across the cable post clamps.
a. If the volta
ge is equal or greater than the
voltage in Table 9, then go to Step 2.
b. The batter
y voltage is less than the voltage in
Table 9.
A low charg
einabatterycanbecausedby
several conditions.
•
Deteriora
tion of the battery
•
A shorted starting motor
•
A faulty alternator
•
Loose driv
e belts
•
Current leakage in another part of the
electrica
l system
2. Measure the current that is sent to the starting
motor sol
enoid from the positive post of the
battery.
Note: If t
he following conditions exist, do not perform
the test in Step 2 because the starting motor has a
problem.
•
The voltage at the battery post is within 2 volts
of the lowest va
lue in the applicable temperature
range of Table 9.
•
The large star
ting motor cables get hot.
Use a suitable ammeter in order to measure the
current. Plac
e the jaws of the ammeter around the
cable that is connected to the “bat” terminal. Refer
to the Specifications Module, “Starting Motor” for
the maximum c
urrent that is allowed for no load
conditions.
The current a
nd the voltages that are specified
in the Specifications Module are measured
at a temperature of 27°C (80°F). When the
temperature
is below 27°C (80°F), the voltage will
be lower through the starting motor. When the
temperature is below 27°C (80°F), the current
through the
starting motor w ill be higher. If the
current is too great, a problem exists in the starting
motor. Repair the problem or replace the starting
motor.
If the current is within the specification, proceed
to Step 3.
3. Measure the voltage of the starting motor.
a. Use the multimeter in order to measure the
voltage of the starting motor, when you are
cranking o
r attempting to crank the engine.
b. If the voltage is equal or greater than the
voltage th
at is given in Table 9, then the battery
and the starting motor cable that goes to the
starting motor are within specifications. Go to
Step 5.
c. Thestartingmotorvoltageislessthanthe
voltage s
pecified in Table 9. The voltage drop
between the battery and the starting motor is
toogreat.GotoStep4.
4. Measure the voltage.
a. Measure
the voltage drops in the cranking
circuits with the multimeter. Compare the
results with the voltage drops which are
allowed
in Table 10.
b. Voltage drops are equal to the voltage drops
that ar
e given in Table 10 or the voltage drops
are less than the voltage drops that are given
inTable10.GotoStep5inordertocheckthe
engine
.
c. The voltage drops are greater than the voltage
drops t
hat are given in Table 10. The faulty
component should be repaired or replaced.