The
importance of detecting
an “open”
diode is that,
in
addition
to the loss of several
amperes of output,
an
open diode
can
lead
to the failure
of other diodes,
resulting
eventually in
a dead battery. In addition,
an
open diode could
cause a voltage
regulator to fail.
A
replacement regulator
would also fail if the
open diode
was
not detected and corrected. T
o avoid the possi bil-
ity of overlooking
this type of defect, the VAT
60
includes a DIODE STATOR
testing mode.
The VAT 60 is
programmed to make
the
necessary
tests
of
a
charging system. Since the battery is a part
of the
charging system, its condition must be con-
sidered when testing the alternator and voltage reg-
ulator.
The condition of the battery determines how
hard
the alternator works and a bad battery can
cause
an alternator
failure.
In
addition, the condition of the starting system,
or
Of the
engine if it is hard to start, can cause a battery
to be run down. Therefore,
any
test
of the charging
System
should include a test of the
battery
and start-
ing system.
CHARGING SYSTEM TEST
See
Figure
4
(page
7
)
for hookup
illustration.
1.
Attach the Black clamp-on AMP PROBE around
vehicle
ground cable or cables.
Be sure
arrow is
pointing away
from
battery terminal.
2.
Setthe FUNCTION SELECTOR to the CHARGING/
DIODE STATOR
position.
3.
Observe tachometer and bring engine speed to
2500 rpm.
4. Adjust
the LOAD CONTROL
KNOB slowly
as
required
to
obtain
the
highest
reading
on the
AMPS
DISPLAY. Perform
this test within 15
seconds.
5.
Rotate
the LOAD CONTROL
KNOB
to
OFF.
f
6.
Continueholdingenginespeedover2000rpmto
\ allow
accurate
voltage regulator reading.
This
occurs when alternator output drops
below 15
N^amps. This could take several
minutes.
7.
Observe
results.
GOOD
—
Alternator/Generator output within 10%
of
manufacturer’s
specification.
BAD
—
Output
not within 10% of specifications.
Perform
OUTPUT TEST USING
TESTER
FIELD
SELECTOR.
CHARGING/DIODE
STATOR
TESTS
The CHARGING/DIODE
STATOR
test position
actually performs three tests:
1. Diode Stator test
2. Maximum Alternator Output
test
3. Voltage Regulator upper
limit cutoff voltage
indication.
Test
sequence
1.
Be
sure
LOAD
CONTROL
KNOB
is fully coun-
terclockwise
to
OFF and
FUNCTION
SELEC-
TOR
is in OFF position.
2. Connect leads
to proper battery terminals
and
AMP
PROBE to proper lead.
See Figure
4
page
7
for
hookup
illustration.
Be
sure to connect
trigger lead as designated
in Figure
4l
3. Set FUNCTION
SELECTOR
to
CHARGING/
DIODE
STATOR position.
4.
Turn headlights, blower,
and
other
accessories
ON
for 10 amp load
minimum.
5. Achieve engine
speed
of 2500 rpm to
begin
testing.
6. Observe DIODE
STATOR
determination
3
seconds into test (DIODE
STATOR
test).
Test
conditions
Current
is at least 10 amps
and rpm is
2500 or more.
7. After DIODE STATOR
determination,
begin
loading the alternator until
a peak
amp reading
is obtained (Maximum
Alternator
Output
test).
NOTE: Operator has 15
seconds to
load alter-
nator
for
peak
amp
reading
after
DIODE STA-
TOR
determination is displayed,
8. Turn off
load.
Observe
displays until
test time
expires.
Testing
automatically continues
until:
a.
current reading is less than
15 amps and/or
b.
voltage is greater than
1 5.8v at an engine speed
of 2000
rpm
or
more.
c.
testing
aborts.
9
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