
RENR9348-01 101
Troubleshooting Section
Turn the battery disconnect switch to the OFF
position.
Restore the wiring to the original configuration.
Expected Result:
Astheengines
peed increases above 75 percent o f
the rated engine speed, the voltage is 24 ± 3 VDC at
the supply wire for each solenoid.
Results:
•
OK – The voltag
eis24±3VDCwhentheengine
speed increases above 75 percent of the rated
engine speed.
Repair: The air shutoff solenoids are receiving
the correct voltage. There may be a problem in
the ground ci
rcuit to the air shutoff solenoids or
the solenoids and/or the valve mechanisms may
not be operating correctly. Perform the following
procedure:
1. Check the ground circuit to the air shutoff
solenoid:
a. Remove the ground wire from the air shutoff
solenoid.
b. Turn the battery disconnect switch to the ON
position.
c. Check continuity of the ground circuit from
the solenoi
dtothebattery.
If continuity does not exist in the ground
circuit to
the air shutoff solenoid, repair
the circuit.
2. Check the m
echanical condition of the valve
mechanisms.
a. Visually i
nspect the mechanical condition of
the valve mechanisms.
b. Manually o
perate the valve mechanisms.
Check that the mechanisms are operating
freely. Check the mechanisms for binding.
If a mechanical problem with the valve
mechanisms is suspected, repair the
mechanis
ms. Replace parts, if necessary.
3. Check the electrical condition of the solenoids:
a. Use 24 ± 3 VDC to test the operation of the
solenoids.
If the s olenoids are not operating
correctly, replace the solenoids.
STOP.
•
NotOK –Thevoltageisnot24±3VDCwhenthe
engine speed in
creases above 75 percent of the
rated engine speed. The air shutoff solenoids are
not receiving the correct voltage. Proceed to Test
Step 9.
Test Step 9. Test the Output Voltage at
the Air Shutoff Relay
A. Remove the wire from the terminal of the air
shutoff relay that is for the secondary output to
the air shuto
ff solenoids.
B. Start the engine.
C. Use Cat ET to activate the “Overspeed Verify”
feature. Wait at least 30 seconds for activation of
the feature
.
D. Increase engine speed to the rated speed of the
engine.
E. As the engine speed increases above 75 percent
of the rated
engine speed, measure the voltage
between the secondary output terminal of the air
shutoff relay and the engine ground stud.
Note: The ECM applies a voltage to the circuit for
approximately one second. Run the test as many
timesasne
cessary in order to verify that a voltage
is present at this output. The emergency stop switch
must be reset before the test can be run again.
F. Stop the engine.
Turn the b
attery disconnect switch to the OFF
position.
Expected
Result:
As the engine speed increases above 75 percent of
the rated
engine speed, the voltage is 24 ± 3 VDC at
the secondary output terminal of the air shutoff relay.
Results:
•
OK – The voltage is 24 ± 3 VDC when the engine
speed inc
reases above 75 percent of the rated
engine speed.
Repair:
The voltage is present at the output of the
relay, but not at the solenoid. There is an electrical
problem in the harness between the air shutoff
relay an
d the air shutoff solenoids. The problem
may be in a connector. Repair the harness and/or
the connectors. Replace parts, if necessary. Verify
that th
e original problem is resolved.
STOP.