Cessna T188C - Page 330

MODEL
188
& T188
SERIES
SERVICE
MANUAL
16-34.
TROUBLE
SHOOTING
THE
ALTERNATOR
SYSTEM
(28
VOLT
SYSTEM)
(Cont.)
b.
ENGINE
RUNNING
(Cont.)
TROUBLE
PROBABLE
CAUSE
REMEDY
ALTERNATOR
MAKES
Shorted
diode
in
alternator.
Turn
off Battery
Switch
and
ABNORMAL
WHINING
remove
"B" Lead
from
NOISE.
alternator.
Check
resistance
from
"B"
Terminal
of
alter-
nator
to
alternator
case.
Re-
verse
leads
and
check
again.
Resistance
reading
may
show
continuity
in one direction
but
should
show
an
infinite
reading
in
the other
direction.
If
an
infinite
reading
is
not
obtained
In at
least
one
direction,
repair
or
replace
alternator.
OVER-VOLTAGE
LIGHT
DOES
Shorted
regulator.
Replace
regulator.
NOT GO
OUT WHEN
ALTER-
NATOR
AND BATTERY
SWITCHES
ARE TURNED
ON.
Defective
over-voltage
sensor.
Replace
sensor.
THRU
18803046
AFTER
ENGINE
START
Regulator
faulty
or high
With
engine
not
running
turn
WITH
ALL
ELECTRICAL
resistance
in
field
circuit.
off
all electrical
loads
and
EQUIPMENT
TURNED
OFF
turn on
battery
and alternator
CHARGE
RATE
DOES
NOT
switches.
Measure
bus
voltage
TAPER
OFF
IN
1-3
MINUTES
to
ground,
then
measure
voltage
from
terminal
of
alternator
to
ground.
If
there
is
more
than
2
volts
difference
check
field
circuit
wiring
shown
on alter-
nator
system
wiring
diagram
in Section
19.
Clean
all
contacts.
Replace
components
until
there
is less
than
2 volts
difference
between
bus
voltage
and field
voltage.
NOTE
Also
refer
to
battery
power
system
trouble
shooting
chart.
ALTERNATOR
SYSTEM
WILL
Alternator
output
voltage
1.
Connect
voltmeter
between
NOT
KEEP
BATTERY
insufficient..
D.C.
Bus
and
ground.
Turn
off
CHARGED.
all electrical
loads.
Turn on
Battery
Switch,
start
engine
and
adjust
for
1500
RPM,
voltage
should
read
approximately
24 volts.
Turn
on
alternator
switch,
volt-
age
should
read between
27.4
and
28.0
volts.
Ammeter
should
indicate
a
heavy
charge
rate which
should
taper
off in 1-3
minutes.
If
charge
rate
tapers
off
very
16-26