Revision 4 - Cessna 172SPHUSR05 Pilot Operating Handbook

SECTION 7
&
AI RPLAN E SYSTEMS D ESC R I PTION
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EXTERNAL POW E R RECEPTACL E
An external power receptacle is i ntegral to the power distribution
mod u le and allows the use of an external electrical power sou rce for
cold weather starting, and d u ring lengthy maintenance work on
electrical and avionics equ ipment. The receptacle is located on the
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left side of the engine cowl ing, j ust forward of the firewall and
m idway up the side.
removing the cover plate (earl ier serial n u mber airplanes) or
opening the h i nged access door (later serial number airplanes) .
The power distri bution module (J-Box) incorporates a circuit
which will close the battery contactor when external power is
applied through the gro u nd service plug receptacle with the master
switch tu rned on. Th is feature is i ntended as a servicing aid when
battery power is too low to close the contactor, and should not be
used to avoid performing proper maintenance procedu res on a low
battery.
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If no avionics equ ipment is to be used or serviced ,
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the avionics master switch should be i n the OFF
position . If mai ntenance is requ i red on the avionics
equipment, use a reg ulated external power source
to prevent damage to the avionics eq u ipment by
transient voltage. Do not crank or start the eng ine
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with the avionics master switch i n the ON positio n .
I Before connecting
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(generator type or battery cart) , the avionics master
switch and the master switch should be tu rned off.
7-36
Access to the receptacle is gained by
NOTE
a n external
CESSNA
MODEL 1 72S
power sou rce

Revision 4