Revision 4 - Cessna 172SPHUSR05 Pilot Operating Handbook

SECTION 7
&
A I R P LAN E SYSTEMS DESC R I PTION
The airplane uses a power d istribution module (J-Box) , located
on the left forward side of the firewal l , to house all relays used
th roughout the airplane electrical system . In additio n , the alternator
control u n it and the external power con nector are housed with i n the
module.
AN N U NCIATOR PAN E L
An annunciator panel (with i ntegral toggle switch) is located on
the left s ide of the i nstru ment panel and provides caution (amber)
and warning (red) messages for selected portions of the airplane
systems. The ann unciator is designed to flash messages for
approximately 1 0 seconds to gain the attention of the pilot before
changi ng to steady o n . The annunciator panel cannot be tur n ed off
by the pilot.
I nputs to the annunciator come from each fuel transmitter, the
low oil pressu re switch , the vac u u m transducers and the alternator
control u nit (AC U ) . Individual LED bu lbs i l l u m i nate each message
and may be replaced through the rear of the annu nciator.
I l l u m i nation i ntensity can be controlled by placi ng the toggle switch
in either the D I M or BRT positions (earlier serial n u m ber ai rplanes)
or the DAY or N I G HT positions (later serial number airplanes) .
The annunciator panel can be tested by placing the Master
switch in the ON position and holdi ng the annu nciator panel test
switch in the TST (earlier serial n u mber airplanes) or the TEST
(later serial n u mber airplanes) position.
messages wil l flas h u ntil the switch is released .
When the Master switch is turned ON, some annu nciators
will flash for approxim ately 1 0 seconds before i l l u m i nating
I
stead ily. When the ann unciator panel test switch is held i n
the TST (earlier serial number airplanes) or the TEST (later
serial n u mber airplanes) position, all remai n i ng lights will
flash u ntil the switch is released .
7-32
All amber and red
N OTE
C ESSNA
MODEL 1 72S
I

Revision 4