B
52
Repair and Service Manual
ELECTRICAL
Read all of SAFETY and this section before attempting any procedure. Pay particular attention to Notices, Cautions, Warnings and Dangers.
10002660
FAULT TESTING
General
Knowledge of use of wiring diagrams and a Digital Volt
Ohm Meter (DVOM) is necessary to effectively determine
fault within the circuits that include the electrical accesso-
ries, lighting, and gauges.
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.
Knowledge of simple logic fault testing will reduce the
number of steps required to isolate the problem.
Example 1: If the vehicle does not start and none of the
lights operate or burn dimly, test the battery before trying
to determine fault within the lighting circuit.
Example 2: If a problem occurs in the lighting circuit that
causes only one of the headlights to fail, it is not neces-
sary to check the battery wiring or the fuse since voltage
is present. Check the headlight that is not operating. If
power is found at the connector and the ground wiring is
satisfactory, it is 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 put the negative (-) probe on the negative bat-
tery terminal. Move the positive (+) probe to each wire ter-
minal starting at the battery and moving out to the device
that is not working. Check both sides of all switches and
fuses.
When no battery voltage is found, the problem is 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 can be used except that
the DVOM is set to continuity. Place the negative (-)
probe on a wire terminal at the beginning of the circuit
and move toward the device that is not working with the
positive (+) probe. When continuity is no longer indicated,
a failed conductor or device is indicated.
Testing Battery Voltage
Determine the condition of the battery set before proceed-
ing with any electrical testing.
An open voltage test is not helpful since a battery that has
deteriorated to the point of requiring replacement can still
show eight volts or higher in an open voltage test.
If there is any doubt as to the adequacy of the battery set,
charge the batteries and perform a load test using a dis-
charge machine following manufacturer’s instructions. If
batteries are satisfactory, recharge battery set.
With the adequacy of the batteries confirmed, use a
DVOM connected directly to the battery terminal posts to
determine the open voltage of the set.
In the following tests, this voltage level will be used as a
reference.
Some loss due to resistance of wires and connectors can
be shown by readings that could be up to one volt less
than battery reference voltage (BRV).
No reading indicates an “open” condition and the battery
wires should be checked for a broken or disconnected
wire or component.
Continuity Check
To prevent possible injury or death
caused by a battery explosion, dis-
connect the electrical power. Use an
insulated wrench to remove the negative (B-) wire
from the battery.
Before removing the negative (B-) wire at the battery,
switch the key switch to the OFF position, then remove
the key from the switch. Always use insulated wrenches
when working on batteries.
To check for continuity, set the DVOM to the K
Ω
setting
and select ‘Continuity’. The meter will give an audible sig-
nal when it detects continuity. If the meter does not have a
continuity setting, set it to K
Ω
, the meter will indicate “0”
when it detects continuity.
Testing A Switch for Continuity
Put one probe on one contact of the switch. Put the sec-
ond probe on the second terminal of the switch (Ref. Fig.
13).
Actuating a normally open (NO) switch causes the DVOM
to show “0”, or gives an audible indication when the
switch is operated. A normally closed (NC) switch causes
the meter to show “0”, or gives an audible indication when
the probes are attached, without activating switch. The
audible indicator will stop and the meter display will show
a value greater than “0” when the switch is activated.
The change in display or audible indicator shows that the
switch is functioning.
Fig. 13 Continuity Check of Switch
Press to
Activate
Switch
BEEP
BEEP
