ELECTRIC SYSTEM 5540F/YB5515 SERVICE MANUAL
3-4 Published 10-21-2010, Control# 198-04
batteries and leaving the other at low charge can
cause damage to the fully charged battery. A weak
battery in the system puts an overload on the
electrical system.
STARTING CIRCUIT
The starting circuit for a diesel engine includes the battery,
starter motor and solenoid, auxiliary start solenoid, starter
relay, park brake switch, and the ignition switch.
The starting circuit for a gasoline or dual fuel engine
includes the battery, starter motor and solenoid, engine ICU
park brake switch, and ignition switch.
General Inspections
Many starting problems can be found by making the
following checks:
1. Check that the parking brake is engaged.
2. Check battery condition. Charge or replace the battery
as necessary. Clean battery posts and cable connectors.
3. Inspect wiring for worn insulation or other damage.
Replace bad wiring. Inspect all connections at the starter
motor, starter solenoid, starter relay (diesel engine), and
wire harness plugs. Clean and tighten all connections
and replace any bad wiring.
4. If the starter still does not operate after correcting the
circuit, perform the Starting Circuit Check.
Starting Circuit Check
NOTE: If the starter will not turn the engine, the following
checks will help find a faulty component in the
starting circuit. Use a test lamp or voltmeter to
perform the checks.
1. Place the ignition switch in the OFF position and
disengage the parking brake.
2. See the electrical schematic at the end of this manual.
Momentarily connect a jumper cable to the “B” and “S”
terminals on the starter solenoid.
a. If the starter operates, the starter and solenoid are
good. The problem is somewhere between the
solenoid and the ignition switch. Go to step 3.
b. If the starter does not operate, connect the jumper
cable to the “B” and “M” terminals on the starter
solenoid. If the starter operates correctly, the
problem is in the starter solenoid. Replace the
solenoid. If the starter still does not operate, the
starter is bad and must be repaired or replaced.
3. Check the voltage at the “BAT” terminal of the ignition
switch. If no voltage is indicated, there are wrong
connections or damage to the wiring between the starter
and the ignition switch. If voltage is indicated, go to step
4.
4. Turn the ignition switch to the START position and check
voltage at the start “ST” terminal. Go to step 5 if voltage
is indicated. If no voltage is indicated, replace the
ignition switch.
5. Make sure that the parking brake is engaged. Have
someone hold the key switch in the START position,
check for voltage at wires 21 and 21A on the neutral start
relay located under the instrument panel. If voltage is
indicated at the relay wire 21A, go to step 6. If there is no
voltage at wire 21, check the wire to the ignition switch. If
there is voltage at wire 21 and no voltage at wire 21A,
replace the relay.
6. Turn the ignition switch to the START position. Connect
a jumper wire between wires 21A and “B” on the starter
solenoid. If the starter operates, the starter relay is
defective and must be replaced. If the starter did not
operate, go to step 7.
7. With the ignition switch in the START position, check for
voltage at the switch “S” terminal of the starter solenoid.
If there is no voltage, the problem is in the wire from the
starter relay to the starter solenoid. Repair or replace the
wiring. If voltage is indicated, the problem is in the starter
solenoid.
Gasoline or Dual Fuel Engines
1. Place the ignition switch in the OFF position and place
the travel select lever in neutral.
2. Refer to the electrical schematic at the end of this
manual. Momentarily connect a jumper cable to the “B”
and “S” terminals on the starter solenoid.
a. If the starter operates, the starter and solenoid are
good. The problem is somewhere between the
solenoid and the ignition switch. Go to step 3.
b. If the starter does not operate, connect the jumper
cable to the “B” and “M” terminals on the starter
solenoid. If the starter operates correctly, the
problem is in the starter solenoid. Replace the
solenoid. If the starter still does not operate, the
starter is bad and must be repaired or replaced.
3. Check the voltage at the “BAT” terminal of the ignition
switch. If no voltage is indicated, there are wrong
connections or damage to the wiring between the starter
CAUTION
The ignition switch must be in the OFF position when
performing steps 1 and 2. If the switch is in the ON
position, the engine may start if the parking brake is
engaged. Personal injury is possible.
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