B
ELECTRICAL
Read all of SAFETY and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
119
Repair and Service Manual
699322
Fig. 9 DVOM
TROUBLESHOOTING
In order to effectively troubleshoot the circuits that
include the horn, lighting, brake/turn signals and gages,
the technician must be able to use the wiring diagram
and a DVOM.
The wiring diagram shows the path followed by a voltage
or signal from its origination point to its destination. Each
wire is indicated by color and is divided into the main har-
ness and the dash harness (Ref. ).
The technician should use simple logic troubleshooting in
order to reduce the number of steps required to isolate
the problem.
Example 1:
If the vehicle will not start and none of the
lights function (or burn dimly) the battery should be
tested before trying to troubleshoot the lighting circuit.
Example 2:
If a problem occurs in the lighting circuit that
results in only one of the headlights not working, there is
no reason to check battery wiring or the fuse since it is
obvious that voltage is present. Since bulbs will burn out
over time, the obvious place to start is at the headlight
that is not functioning. If power is present at the connec-
tor and the ground wiring is satisfactory, the only possibil-
ities that exist are a burned out bulb or a poor contact
between the connectors and the headlight.
If power is not present but the other headlight functions,
a wiring problem is indicated between the two headlights.
In some cases where battery voltage is expected, the
easiest way to test the circuit is to set the DVOM to DC
volts and place the negative (-) probe of the DVOM to the
negative battery terminal. Move the positive (+) probe to
each wire termination starting at the battery and working
out to the device that is not working. Be sure to check
both sides of all switches and fuses.
When no battery voltage is found, the problem lies
between the point where no voltage is detected and the
last place that voltage was detected. In circuits where no
voltage is expected, the same procedure may be used
except that the DVOM is set to continuity. Place the neg-
ative (-) probe on a wire terminal at the beginning of the
circuit and work towards the device that is not working
with the positive (+) probe. When continuity is no longer
indicated, a failed conductor or device is indicated
POWER SUPPLY
Tool List
Qty.
DVOM ......................................................................... 1
1. Check for loose or bare wires
Check for loose wires at each terminal connection
and for worn insulation or bare wires touching the
frame.
Bare wires may cause a short circuit
.
NOTICE: If any DVOM readings indicate a faulty
wire, it is recommended that the condition of the
terminals and wire junction be examined. A faulty
wire should be replaced with one of the same
gauge and color and wired between the correct
components and wire tied to the harness bundle.
The faulty wire should be cut back close to the har-
ness and the ends protected with vinyl electrical
tape.
2. Check battery condition
Check for adequate battery volts (nominal 12 VDC)
by setting DVOM to 30 VDC range and place the red
probe (+) on the battery post with the green wire
attached. Place the black probe (-) on the battery post
with the black wire attached. A reading of 11 VDC or
greater indicates adequate battery condition. No
reading indicates (a) a poor connection between the
probes and the battery terminals; (b) a faulty DVOM.
A voltage reading below 11 volts indicates poor bat-
tery condition and the vehicle should be recharged
before proceeding with the test.
NOTICE: Due to the resistance of the wires involved
within the harness, voltage readings may be some-
what lower than battery voltage. A reading of 1 volt
below battery voltage is acceptable.
3. Check power wire
Firmly attach the black probe (-) to the battery post
with the black wire attached and the red probe (+) to
the green wire terminal at the fuse block. A reading of
COVER
DATA-H
SWITCH
RANGE
SWITCH
TRANSISTOR
SOCKET
+ TEST LEAD
- TEST LEAD
TEST
RECEPTACLES
FUNCTION
SELECTOR
SWITCH
CONTINUITY
TEST DIODE
TEST, AC/DC
CURRENT
TOGGLE
SWITCH
DIGITAL
DISPLAY
