Cessna T188C - Electric Fuel Pump Circuit (A188 Series)

MODEL
188
&
T188
SERIES
SERVICE
MANUAL
d. Adjust
relay
as
required
to obtain
a 31.
5 volt
nuisance
trip-outs
caused
by voltage
spikes
or
tran-
pull-in.
Seal
adjusting
screw.
sients.
e. Reinstall relay on aircraft.
16-44. REMOVAL AND INSTALLATION. (See CAUTION
figure
16-5.)
Grounding
the orange lead or interconnecting
a. Open battery box and disconnect ground cable orange and black leads will destroy the sensor.
from the negative
battery terminal.
Pull cable
clear
of battery box.
16-47. ALTERNATOR
FAILURE
WARNING CIRCUIT.
b. Tape
and lable wires connected
to the three ter-
THRU 1977 MODELS.
minals on relay before removal. Remove screws
and
locking washers holding wires
on relay connec- 16-48.
DESCRIPTION. A silicon, junction,
power
tions.
diode is wired
in series with the alternator
output
c. Remove
screws and
locknuts securing
relay to
lead. A 28-volt
reed type
relay is connected
across
firewall.
The relay will now be free for
removal, the diode. On
normal operation the diode
is in for-
d. To replace
relay, reverse
this procedure.
ward conduction
and the relay
sees about l-volt
drop
across the diode and remains de-energized. If the
CAUTION
alternator
output should
fail, bus
voltage will
exceed
alternator
output energizing
the relay
and directing
Observe
polarity
when
replacing
capacitor
power
to
the alternator
out
warning
lights
on
the
in-
on
relay.
strument
panel.
The diode
assembly
is mounted
on
the
left hand
side of
the firewall.
16-45.
OVER-VOLTAGE
WARNING
CIRCUIT.
(AIRCRAFT
SERIAL
18800833
THRU
18803046,
16-49.
REMOVAL
AND
INSTALLATION.
(See
14-VOLT
SYSTEM).
figure
16-5.)
a. Disconnect the four leads from the alternator
16-46.
DESCRIPTION.
The
over-voltage
warning
warning
assembly
and
tag wires
for reinstallation.
system
consists
of an
over-voltage
sensor
switch
b. Remove
screws,
spacers
and nuts
securing
the
and a
red warning
light
labeled,
"HIGH
VOLTAGE",
warning
assembly
to
the firewall
and remove
assem-
on the
instrument
panel.
When
an
over-voltage
bly.
tripoff
occurs
the
over-voltage
sensor
turns
off
the
c. Remove
the
four
screws
securing
the
diode
alternator
system
and
the
red warning
light comes
assembly,
then remove
the bolt
securing
the wires
on. The
ammeter
will
show
a discharge.
Turn
off
on the
forward
side of
the diode
and
the nut
and
both sections
of the Master
Switch
to
recycle
the
washers
on
the aft
side and
remove
assembly.
over-voltage
sensor.
If the over-voltage
condition
d.
For reinstallation
reverse
the
preceding
steps.
was
transient,
the normal
alternator
charging
will
e.
When installing
new
diode on
heat sink,
coat
resume
and no
further action
is necessary.
If the
bottom
surface of
diode hex
with Dow-Corning
DC-4
over-voltage
tripout recurs,
then a generating
sys-
or a similar
heat sink compound.
Torque
diode to
tem
malfunction
has occurred
such
that the
electrical
50 lb.
inches.
accessories must be operated from the aircraft bat-
tery only.
Conservation of electrical energy
must be 16-50. ELECTRIC
FUEL PUMP CIRCUIT.
(See
practiced until the flight can be terminated. The Section 12.)
over-voltage
red warning
light filament may
be tested
at any time by turning off the "Alternator" portion of 16-51. AUXILIARY ELECTRIC FUEL PUMP FLOW
the Master Switch and leaving the "Battery" portion RATE ADJUSTMENT. See Section 12.
turned
on. This
test does not induce
an over-voltage
condition on the electrical system. The sensor is 16-52. AIRCRAFT LIGHTING SYSTEM.
preset and not adjustable. The sensor is located on
the right
hand side
of the instrument
panel,
attached
16-53.
DESCRIPTION.
The aircraft
lighting
system
to the wire
bundle
with
a sta-strap.
A
capacitor
is
consists
of
landing
and taxi
lights,
navigation
lights,
also installed
at the same
location, connected
be-
anti-collision
strobe lights,
flashing beacon,
instru-
tween the
circuit
breaker
and the
switch,
to prevent
ment
lighting,
wing
tip turning
lights,
forward
facing
spray lights,
hopper quantity
light and compass
light.
SHOP
NOTES:
16-36