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10-6
TROUBLE DIAGNOSIS
ELECTRICAL SYSTEMS
(2
82)
SECTION 10-B
ELECTRICAL TROUBLE DIAGNOSIS
CONTENTS OF SECTION 10-B
Parag
raph
Subject
Page
Paragraph
Subject
Page
10-7
Battery
a
I!d C
a bles-Trouble
10-11
Lighting System-Trouble
D
iagnosis
.
. .. ..
....
. . ..
.
.
10
-6
Diagnosis
..
..
. .
.....
..
. ..
10-10
10-8
Gen~ratin~
System-Trouble
10-12
Sign~ling
Systems-e-Trouble
Diagnosis
.
.. . . .
.
.
..
..
..
.
.
10-7
Diagnosis
.
. . .
.
..
.
. .
.
.. . . .
10-10
10-
9
Cranking Sestem-s-Trouble
10-13
Instruments a
n d Clock-
Diagnosis
.
..
..
..
.. .... ..
..
.
10-8
Trouble
Diagnosis
.
.
.
.. .
.
.
10
-11
10
-10
Ignition System - T ro u ble
Diagnosis
.
.
. . .
..
.. . .
.
. . ..
10-9
SERVICE BULLETIN REFERENCE
Bulletin No
.
Page No.
SUBJECT
10-7
BATTERY AND CABLES-TROUBLE
DIAGNOSIS
a. Quick Check of Battery and Cables
Whenever
elect r ical trouble develops it is
desirable to make a quick
check
of. the battery
and cables to make
certain
that this source of
current is in good condition, securely connected,
and is functioning properly. This check will also
gi ve a good check on the cranking
system.
1. Turn on the lights. They should burn
steadily and with normal brilliance.
2. With lights burning, operate the crank-
ing motor. Either have the headlights shining
on a wall so their brilliance can be noted, or
have someone watching the headlights.
3.
When cranking motor solenoid switch is
closed, one of four things will normally happen:
(1)
the lights will stay bright and engine will
be cranked at normal sp
eed;
(2) the lights will
go out; (3) lights will dim considerably; (4)
lights will stay bright but no cranking action
will take place. The first named condit ion indi-
cates that there is nothing wrong with
the bat-
tery,
cables,
and cranking system. The other
conditions indicate trouble as follows:
4. If lights go out as cranking motor sole-
noid switch is closed, it indicates a poor connec-
.ion in the circuit between battery and cranking
notor. Check battery cables and clean and
.ighten loose or corroded terminals (par. 10-21)
.
5. If
lights dim considerably
as cranking
motor solenoid switch is closed
,
it indicates that
the battery is run down, or
there
is a condit ion
in cranking
mot or
or engine which causes an
excessive current drain on the
battery.
A low
battery
will be
indicated by
a clatter ing noise
in cranking motor solenoid because the
battery
cannot sustain
the voltage required
t
o
hold
solenoid
plunger
"in"
after
switch contacts
close and the "pull in" winding is shorted out.
Test battery with
hydrometer (par .
10-19) and
gi ve ita high discharge test (par. 10-20).
If
battery is found to be in good condition check
cranking motor (par. 10-36)
.
6. If lights stay bright but no cranking
action
occur
s
when cranking motor solenoid
switch is closed, it indicates an open circuit in
cranking motor, switch, or control
circuit.
See
paragraph 10-9.
b. Undercharge Failure of Battery
The most frequent trouble experienced with
storage batteries
is
failure
to maintain a
state
of
charge
sufficient to crank the
engine
and also
furnish current to the ignition
system,
lights
and accessories. Failure to maintain a proper
state of charge may be due to one or more of
the following conditions.
1.
Operating Conditions. When determin-
ing cause of premature failure of a battery,
i
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