Cessna T188C - Page 320

MODEL
188
& T188
SERIES
SERVICE
MANUAL
Inspect the cleaned box and
cover for physical dam-
16-25. RADIO PROTECTION
DIODE.
age and for areas lacking proper acid proofing. A
badly
damaged
or corroded
box should
be replaced.
16-26.
DESCRIPTION.
A silicon
diode
is installed
If the box
or lid require
acid
proofing,
paint the
area
across the
winding
of the battery
contactor
to sup-
with
acid-proof
black
lacquer,
part
no.
CES1054-381,
press
the inductive
"kick"
created
when
the
contactor
available
from the
Cessna Supply
Division.
is de-energized.
The
diode is
shown in figure
16-2.
Reducing
the inductive
peak voltage
flowing back
onto
16-20.
BATTERY CONTACTOR.
the bus
system prevents
possible damaging
of the
transistors
in any radio
equipment turned
on.
16-21. DESCRIPTION.
The battery
contactor is
bolted to
the firewall
adjacent to the
battery box on
16-27.
GROUND SERVICE
RECEPTACLE.
the
A188B
and thru
18803721T
on
the battery
box on
the T188C.
Beginning with
T18803721T
the contactor
16-28. DESCRIPTION.
(See
figure 16-3.)
A ground
is mounted
on a bracket adjacent
to the battery.
The
service is offered
as optional
equipment to
permit
contactor is a solenoid plunger
type, which is actu-
use of external power for cold
weather starting or
ated by
turning the
master switch
on.
When the
mas-
when performing
lengthy
electrical
maintenance.
A
ter switch
is off, the
battery is
disconnected
from
the reverse
polarity
protection
system
is utilized
where-
electrical
system.
A silicon
diode is used
to elimi-
by
ground power
must
pass through
an external
power
nate spiking
of the
transistorized
radio
equipment.
contactor
to be connected
to the
bux. A
silicon junc-
The
cathode
(+) terminal
of the diode
connects
to
the
tion diode
is
connected
in series
with
the coil
on the
battery
terminal
of the battery
contactor.
The
anode
external
power
contactor
so
that if
the ground
power
(-) terminal
of the
diode
connects
to
the same
termi-
source
is inadvertently
connected
with
a reverse
nal
on the
contactor
as the
master
switch
wire.
This
polarity,
the
external
power
contactor
will
not close.
places
the diode
directly
across
the contactor
solenoid
This
feature
protects
the
diodes
in the
alternator,
coil
so that
inductive
spikes
orginating
in
the coil
are
and other
semi-conductor
devices,
used in
the air-
clipped
when
the
master
switch
is opened.
Beginning
craft
from
possible
reverse
polarity
damage.
with
18801069
a vented
contactor
is installed.
NOTE
16-22.
REMOVAL
AND
INSTALLATION.
(See figure
16-2.)
Maintenance
of the
electronic
installation
a. Disconnect
ground
cable
from
negative
battery
cannot
be
performed
when
using
external
terminal.
Pull
cable clear
of battery.
power.
Application
of
external
power opens
b.
Remove the
nut, lockwasher
and the two
plain
the relay supplying
voltage to
the electronic
washers
securing
the
battery
cables
to the
battery
bux.
For
lengthy
ground
testing
of
electron-
contactor.
ic
systems,
connect
a well
regulated
and
c.
Remove
the nut,
lockwasher
and the
two plain
filtered
power supply
directly
to the
battery
washers
securing
the
wire
which
is routed
to the
side
of the
battery
contactor.
Adjust
the
master
switch.
supply
for 14
or 28-volts,
depending
on 14
d.
Remove
the
bolt,
washer
and
nut
securing
each
or 28-volt
system,
and
close
the
master
side
of
the
battery
contactor
to the
firewall
on the
switch.
A188B
and
the
battery
box/bracket
on the
T188C.
The
contactor
will
now
be
free
for removal.
NOTE
e.
To replace
the
contactor,
reverse
this proce-
dure.
On
Aircraft
Serials
18803047
thru
18803071
refer
to Cessna
Single-engine
Service
Let-
16-23.
BATTERY
CONTACTOR
CLOSING
CIRCUIT.
ter SE78-19,
dated
March
27, 1978.
-16-24.
DESCRIPTION.
Beginning
with aircraft se-
The following
check,
to verify the condition
of the
rial 188-0318.
An inline
fuse
and a
resistor
are in-
battery,
should
be made
after
start
and removal
stalled from
the positive
side of the
battery to the
of
the external
power source.
small
lug on the
ground
service
receptacle.
(See
1. Master
Switch
- OFF.
figure
16-2.) When
the aircraft
battery
is low
and
2.
Taxi and
Landing
Light Switches
- ON.
an
external
power source
is being
used
to start the
3.
Engine RPM
- REDUCE
to
idle.
engine,
ensure
that the master
switch
is "ON"
before
4.
Master Switch
- ON
(with taxi
and landing
disconnecting external
power.
lights on).
5.
Engine
RPM
- INCREASE
to approximately
1500 RPM.
6. Ammeter
and
Low-Voltage
Warning
Light
-
CHECK.
NOTE
If the ammeter
does
not show a
charge or
the low-voltage
warning
light does
not go
out,
the
battery
should
be
removed
from
the
airplane and
properly
serviced prior
to flight.
16-16
Revision
1