(Table 14, contd)
Battery post
“
+
”
to the
terminal of the starting
motor solenoid
“
+
”
0.5 volts
1.0 volts
Solenoid terminal
“
Bat
”
to the solenoid terminal
“
Mtr
”
0.4 volts
0.8 volts
Voltage drops that are greater than the amounts in
Table 14 are caused most often by the following
conditions:
• Loose connections
• Corroded connections
• Faulty switch contacts
Diagnosis Procedure
The procedures for diagnosing the starting motor are
intended to help the technician determine if a starting
motor needs to be replaced or repaired. The
procedures are 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 cranking 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 attempting to crank the engine. Do not measure
the voltage across the cable post clamps.
a.
If the voltage is equal or greater than the
voltage in Table 13 , then go to Step 2.
b.
The battery voltage is less than the voltage in
Table 13 .
A low charge in a battery can be caused by
several conditions.
• Deterioration of the battery
• A shorted starting motor
• A faulty alternator
• Loose drive belts
• Current leakage in another part of the
electrical system
2.
Measure the current that is sent to the starting
motor solenoid from the positive post of the battery.
Note:
If the 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 value in the applicable
temperature range of Table 13 .
•
The large starting motor cables get hot.
Use a suitable ammeter in order to measure the
current. Place 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 current that is allowed for no load
conditions.
The current and 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 will 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 or attempting to crank the engine.
b.
If the voltage is equal or greater than the
voltage that is given in Table 13 , then the
battery and the starting motor cable that goes
to the starting motor are within specifications.
Go to Step 5.
c.
The starting motor voltage is less than the
voltage specified in Table 13 . The voltage
drop between the battery and the starting
motor is too great. Go to Step 4.
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 14 .
b.
Voltage drops are equal to the voltage drops
that are given in Table 14 or the voltage drops
are less than the voltage drops that are given
in Table 14 . Go to Step 5 in order to check the
engine.
c.
The voltage drops are greater than the voltage
drops that are given in Table 14 . The faulty
component should be repaired or replaced.
52
UENR0617
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