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GM COACH MAINTENANCE MANUAL
Sec.
21
Page. 205
The information in this section
includes trouble symptoms which
might be encountered and their
probable causes.
No attempt is
made to outline detailed repair
instructions, as these instructions
are included in various sections
of this Maintenance Manual.
Causes of trouble symptoms
in
any
automotive vehicle may
be varied; therefore, a hit-and-
miss
search would result in a
tedious guessing contest,
Proper
diagnosis
of
symptoms
is
an
orderly process
of eliminating
the causes of the symptoms.
An
M•orderly process "means to check
the
most
probable or common
cause
first,
then proceed with
the next probable cause.
Additional publications which
cover these units are as follows:
Unit
'DTesel Engine . .
Air Conditioning
Form No.
X-5014A
X-5028
ELECTRICAL
SYSTEM
TROUBLE
This paragraph includes only
those
symptoms
which
might
occur
in the
starting
system,
battery, generator and regulator,
and lighting system,
STARTER
If the
engine fails to start
after
repeated
and satisfactory
operations of the starter, cause
of failure cannot be attributed to
the starting system, but to other
functioninc systems of the engine.
Starter Fails to Operate
1. Low battery.
2. Loose
or broken battery
or ground cables.
3. Starter
solenoid contacts
corroded
or burned, preventing
a good contact.
4, If, after making the above
corrections, the starter still fails
to operate, overhaul and repair
or replace.
Starter Noisy
1. Loose mounting.
2. Insufficient lubrication.
3. If
starter is still noisy,
it is in need of an overhaul and
must be
repaired or replaced.
Slow Cranking Speed
1. Heavy engine oil in a cold
engine.
2. Weak
battery
or
loose
cable connections.
3. Excessive
resistance
in
circuit.
Perform
line
voltage
tests.
4.
If the starter still operates
slowly
after
making
the above
corrections, overhaul and repair
or replace.
BATTERY
Discharged
1. Terminals
may be loose
or corroded.
2. Low water in cells.
3. Shorted cells,
4. Defective generator.
5. Improper regulator adjust-
ment.
Test, adjust, or replace.
Overheating
Regulator defective or in need
of adjustment,
GENERATOR AND REGULATOR
Since generator and regulator
functions
are
directly
related,
both
units
must be considered
when checking trouble symptoms
in generator circuit.
When the
ammeter shows an unsatisfactory
reading, make sure ammeter is
correct before
making
repairs
on generating system,
High Charging Rate With
Fully Charged Battery
1. Check
ground wire from
generator to regulator for damage
or loose connections,
2. Clean and tighten all the
terminals and connections in the
generator circuit.
3. If
condition
still
exists,
either
voltage
regulator
is
in
need of adjustment, or generator
is in need of an overhaul.
Low or No Charging Rate
With Low Battery
1. Check
all wires between
generator and regulator for worn
insulation or other damage.
2. Loose fan belt.
When trouble is encountered
in
these
units always refer to
the applicable publication,
The following procedures are
grouped
to
permit
a
practical
diagnosis
of trouble symptoms.
In
many
instances, a
symptom
indicating trouble in one unit may
be
caused
by a difficulty in a
closely related unit or system.
When repairs or adjustments
are
required,
reference should
be
made
to
applicable
manual
section for detailed procedures.
SHOOTING
3.
If this
does not correct
the trouble, either the generator
or regulator, or both, must be
replaced.
Noisy Generator
1, Loose generator mounting.
2. If noise is still present,
repair or replace generator.
LIGHTING SYSTEM
Reference to lighting circuit
diagram will show that a single
circuit
from
battery
to
gang
switches is common to all lights.
At gang switches, single circuit
is divided into multiple circuits,
each
common
to its particular
circuit.
These circuits are then
taken to
junction points where
they are divided into individual
circuits, each taken to a single
light. Return path of each circuit
is
through
ground
to
battery.
Dividing circuits in this manner
provides a convenient and logical
method of locating the source of
trouble.
The use of a voltmeter
or trouble lamp, and adherence
to
the following principles will
aid
in
locating
trouble
in the
lighting system,
1, Source of trouble common
to all lights will be located in
that part of the circuit common
to all lights.
2, Source of trouble common
to one or more -
but not all-
lights will be located in that part
of the
circuit common only to
flll
the lights affected.
3. Source
of
trouble
at
a
single light will be confined to
the individual circuit of the light
affected.
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