Cessna Skyhawk 172N Pilot Operating Handbook page 161

PILOT'S OPERATING HANDBOOK GROUND SERVICE PLUG
SUPPLEMENT
RECEPTACLE
MODEL 172N
SUPPLEMENT
GROUND SERVICE
PLUG RECEPTACLE
SECTION 1
GENERAL
The ground service plug receptacle permits the use of an external
power source for cold weather starting and lengthy maintenance work on
the electrical and electronic equipment. The receptacle is located behind a
door on the left side of the fuselage near the aft edge of the cowling.
NOTE
If
no avionics eqUipment is to be used or worked on, the
avionics power switch should be turned off.
If
maintenance
is required on the avionics equipment. it is advisable to
utilize a battery cart external power source to prevent
damage to the avionics equipment by transient voltage. Do
not crank or start the engine with the avionics power
switch turned on.
The battery and external power circuits have been designed to com­
pletely eliminate the need to "jumper" across the battery contactor to close
it
for charging a completely "dead" battery. A special fused circuit in the
external power system supplies the needed "jumper" across the contacts
so that with a "dead" battery and an external power source applied, turning
the master switch ON will close the battery contactor.
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1
July 1978
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