Cessna T188C - Page 321

MODEL
188
& T188
SERIES
SERVICE
MANUAL
16-29.
TROUBLE
SHOOTING.
TROUBLE
PROBABLE
CAUSE
REMEDY
STARTER
ENGAGES
WHEN
Shorted
or
reversed
diode
in
Check
wiring
to,
and condition
GROUND
POWER
IS
CON-
split
bus-bar
system.
of
diode mounted
on the
split
NECTED.
bus
relay
bracket
adjacent
to
the
magneto
switch.
Correct
wiring.
Replace
diode
board
assembly.
GROUND
POWER
WILL NOT
Ground service
connector
1. Check
for voltage
at all
CRANK
ENGINE.
wired
incorrectly.
three
terminals
of external
power
contactor
with ground
power
connected
and
master
switch
off.
If voltage
is
pre-
sent on
input and
coil termin-
als
but not
on the
output
ter-
minal,
proceed
to
step 4.
If
voltage
is
present
on the input
terminal
but
not on
the coil
terminal,
proceed
to
step
2.
If voltage
is present
on all
three
terminals,
check wiring
between
contactor
and
bus.
2.
Check for
voltage
at small
terminal
of ground
service
re-
ceptacle. If voltage is not pre-
sent,
check
ground
service
plug
wiring.
If voltage
is present,
proceed to step 3.
Open
or
mis-wired
diode
on
3.
Check
polarity
and continuity
ground
service
diode
board
of
diode
on diode
board
at
rear
assembly.
of ground
service
receptacle.
If
diode
is open or
improperly
wired,
replace
diode board
assembly.
Faulty external power
con-
4. Check resistance
from small
tactor. (coil) terminal of external power
contactor
to ground
(master
switch
off
and ground
power
unplugged).
Normal indication is 16-24 ohms.
If resistance
indicates
an open
coil, replace
contactor.
If
resistance
is normal,
proceed
to step 5.
Faulty
contacts in external
5.
With master switch
off and
power
contactor.
ground
power applied, check
for
voltage drop between two large
terminals
of
external
power
(turn on taxi light for a load).
Normal indication is zero volts.
If voltage
is
intermittently
pres-
ent
or present
all the
time,
replace contactor.
16-17