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PART
13-1-GENERAL CHARGING SYSTEM SERVICE
13-11
FIG. 16- Rectifier Pack Lucas
TESTING
THE
DIODES
AND
(RECTIFIER ASSEMBLY)
In the event
of a fault in one or
more of
the
diodes being
indicated by
the.
alternator
output test,
the recti-
fier pack must be removed
from the
alternator.
There are
two
main possibilities
which can destroy
a
diode
during
service, either
a
break-down
in resis-
tance
to
current flow
caused
by
high
current
flow and high
temperature,
or an open
circuit in
both directions
almost always the
consequence of
excess voltage.
CONNECTION
!CATHODE)
CURRENT FLOW
1
HOUSING
FIG. 17 -Diode Connections
For testing purposes
it
is not
necessary to disconnect
the individual
diodes, however
it
is essential that the
stator leads be unsoldered
from the
rectifier pack.
A 12 volt battery with test probes
and a 2 watt globe
in
series
is
used
for diode testing.
POWER DIODES
I
.
Apply one
probe
to the
diode
terminal strip (Lucas)
or
junction
(Bosch) and the
other probe
to
the
appropriate heat
sink.
2.
Reverse
the
probes.
The test
lamp should light in one
direction
only.
Should the lamp light
in
both directions the diode is short
circuited. (If
both diodes of one
phase
are
short
circuited all 6 diodes
will
show a short circuit when tested).
If the
test lamp does not light
in either
direction the diode is open
circuited.
Take apecial
care
ot
the
..
aolder connection•
FIG. 18 -Bosch Rectifier Pack
FIELD DIODES
1. Place
one test probe on the
diode
terminal
strip (Lucas) or
junction
(Bosch) and the other probe
on the
IND terminal (Lucas) or A
terminal
(Bosch) (Figs. 16
&
18).
2.
By
reversing the probes it can
be established
if one or more of the
field
diodes
has failed due to an
open
or short
circuit.
HEAT SINKS
The Negative
heat sink is grounded
to
the
alternator
frame.
The Positive
heat sink is insulated
from the alternator
frame and from
the
Negative
heat
sink.
NOTE: The
Bosch rectifier is not
repairable and
if found faulty in the
foregoing tests
it must be replaced.
The
Lucas rectifier is .serviced in
three subassemblies.
I. Positive diode
and heat sink
assembly.
2. Negative
diode and heat sink
assembly.
3.
Field
diode
and
insulator
assembly.
BATTERY TESTS AND
CONCLUSIONS
Tests
are made on a battery to
determine the state of charge and
also
the
condition.
The ultimate re-
sult
of
these tests is to show that
the battery is good, needs recharg-
ing, or must be
replaced.
If
a
battery
has failed, is low in
charge,
or
requires water
frequent-
ly,
good service
demands that the
reason
for this condition be found.
It
may
be necessary
to follow
trouble shooting procedures to lo-
cate the
cause
of
the
trouble.
(Sec-
tion
1.
in this
part)
.
Hydrogen
and oxygen gases are
produced
during
normal
battery
Poeitive
Heat Sink
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