
RENR9348-01 99
Troubleshooting Section
2. Turn the battery disconnect switch to the ON
position.
3. Measure the voltage between the wires for
these termina
ls.
4. Turn the battery disconnect switch to the OFF
position.
Ifvoltageis24±3VDC,theproblemisintheair
shutoff timer
. Replace the air shutoff timer. Verify
that the repair resolved the original problem.
If voltage is
not 24 ± 3 VDC, the problem is in
the supply c ircuit or the ground circuit for the
air shutoff timer. Check that the circuit breaker for
the ECM rel ay
has not tripped. Repair the circuit.
Replace parts, if necessary. Verify that the repair
resolved the original problem.
STOP.
Test Step 5.
Check the H arness Between
the Timer an
d the Air Shutoff Relay
A. Remove the wire connection from the control input
at the air sh
utoff relay.
B. Turn the battery disconnect switch to the ON
position.
C. Connect a voltmeter between the loose end of the
wire at the
air shutoff relay and the engine ground
stud.
D. As the emer
gency stop switch is activated,
measure the voltage between loose wire at the air
shutoff relay and the engine ground stud.
E. Check the voltage in the circuit as you place the
emergency stop switch in the STOP position.
Note: The timer applies a voltage to the control input
for approximately 2.5 seconds. Run the test as many
timesasn
ecessary 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.
Place the emergency stop switch in the RUN position.
Turn the
battery disconnect switch to the OFF
position.
Restore
the wiring to the original configuration.
Expected Result:
The voltage is 24 ± 3 VDC for 2.5 seconds after the
emergency stop switch is activated.
Results:
•
OK –Thevoltageis24±3VDCfor2.5seconds.
The harness between the timer and the relay is
OK. The proble
m is with the air shutoff relay’s
secondary circuit or the relay. Proceed to Test Step
8.
•
NotOK –Thevoltageisnot24±3VDCfor2.5
seconds.
Repair: There is voltage at the output of the
timer but not at the control input of the relay. The
problem is in
the harness between the air shutoff
timer and the air shutoff relay. The problem may
be in a connector. Repair the harness and/or the
connector. R
eplace parts, if necessary. Verify that
the original problem has been corrected.
STOP.
Test Step 6. Check the Harness Between
the Air Shutoff Relay and t he ECM
A. Remove the wire connection from the control input
at the air shutoff relay.
B. Turn the battery disconnect switch to th e ON
position.
C. Start the engine and allow the engine to run at
low idle.
D. Use Cat ET to activate the “Overspeed Verify”
feature. Wait at least 30 seconds for activation of
the featu
re.
E. Increase engine speed to the rated speed of the
engine.
F. As the engine speed increases above 75 percent
of the rat
ed engine speed, measure the voltage
between the loose wire at the air shutof f relay and
the engine ground stud.
G. Stop the engine.
Turn the b
attery disconnect switch to the OFF
position.
Restore
the wiring to the original configuration.
Expected Result:
As the engine speed increases above 75 percent of
the rated engine speed, the voltage is 24 ± 3 VDC.