Textron Cessna 172R, Pilot Operating Handbook

Page: 256 / 500

SECTION 7
AIRPLANE
&
SYSTEMS DESCRIPTION
CESSNA
MODEL 172R
EXTERNAL
POWER RECEPTACLE
An
external power receptacle is integral
to
the power distribution
module and allows the use
of
an external electrical power source
for
cold weather starting, and during lengthy maintenance work on
electrical
and avionics
equipment.
The receptacle is located on the
I
left side of the engine cowling, just forward
of
the
firewall
and
midway up the side. Access
to
the receptacle is gained by
removing the cover plate (earlier serial number airplanes) or
opening the hinged access door (later serial
number airplanes).
The power distribution
module (J-Box) incorporates a circuit
which
will close the battery
contactor
when external power is
applied through the
ground service plug receptacle with the
master
switch turned on. This feature is intended as a servicing aid when
battery power is
too low to
close the
contactor,
and should
not
be
used
to
avoid performing proper maintenance procedures on a low
battery.
NOTE
•
If no avionics equipment is
to
be
used
or
serviced,
the avionics
master
switch should be in the
OFF
position. If maintenance is required on the avionics
equipment, use a regulated external power
source
to prevent
damage
to
the avionics
equipment by
transient voltage. Do
not
crank or
start
the
engine
with the avionics master switch in the ON position.
•
Before
connecting
an
external power source
(generator type
or battery
cart), the avionics
master
switch and the
master switch should be turned off.
7-36 Revision 8
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