578 8 DIAGNOSTIC TOOLS AND ACCESSORIES
Figure 563 FLUKE 88 in duty cycle mode with
positive trigger slope
3. In duty cycle mode, press the ALER T button to
change from negative to positive trigger slope.
The slope is indicated by a plus or minus sign
below TRIG in the lower left hand corner of the
screen. A percent sign will appear on the upper
right hand corner of the screen.
4. After the meter has been set to the correct
settings, connect meter as indicated in Pin-Point
Diagnostics.
Troubleshooting
1. Verify the problem.
Operate the com plete sys te m and list all
symptoms as follows:
• Check the accuracy and completeness of the
complaint.
• Learnmorethatmightgiveacluetothe
nature and location of the problem.
• Analyze what parts of the system are working.
2. See Section 7 in this manual or the correct chassis
manual.
Read the electrical operation for the problem
circuit and review the circuit diagram.
Understanding electrical operation and the
circuit diagram can narrow the cause of the
problem to one component or certain parts of the
circuit.
3. Check the circuit diagram.
Check the circuit diagram for possible clues to the
problem. Location of specific components in the
circuit will help identify the source of the problem.
Circuit diagrams are designed to make it easy
to identify co mmon points in circuits. This helps
to narrow the problem to a specific area. For
example, if several circuits fail at the same time,
check for a common power source or common
ground connection (i.e., V
REF
, signal ground,
actuator power, actuator ground).
If part of a circuit fails, check the connections
between the part that work s and the part that
does not work. For example, if the low-beam
headlights work, but both high-beam headlights
and the high-beam indicator do not work, the
power and ground paths must be good. Since the
dimmer switch is the component that switches the
power to the high-beam headlights, it is probably
the cause of failure.
4. Determine the cause of the problem and follow
diagnostic procedures in S e c t ion 7.
5. Make the rep air.
Repair the problem circuit as direc ted in the
diagnostic tables
6. Verify that the repair is complete.
Operate the system. Check that the repair has
removed all symptoms and that the repair has not
caused new symptoms.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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