Low Voltage Annunciation; C I Rcuit Breakers And Fuses; Revision 4 - Cessna 172SPHUSR05 Pilot Operating Handbook

C ESSNA
MOD E L 1 72S
lOW VOLTAGE AN N U NCIATION
The low voltage warning annu nciator is incorporated in the
ann unciator panel and activates when voltage fal ls below 24.5 volts.
If low voltage is detected, the red ann unciation VOLTS wil l flash for
approxi mately 1 0 seconds before i l l u m i nating steadily. The pilot
cannot turn off the annunciator.
In the event an overvoltage condition occurs, the alternator
contro l u n it automatical ly opens the AL T FLO circuit breake�
removing alternator field cu rrent and sh uttin g off the alternator. Th
battery wil l then supply system current as shown by a d ischarge
rate on the ammeter. U nder these conditions, dependi ng on
electrical system load , the low voltage warning annunciator will
i l l u m i nate when system voltage drops below normal . The alternator
control u n it may be reset by resetting the circuit breaker. If the
voltage warning
charg i ng has resu med ; however, if the ann unciator i l l u m inate
again , a m alfunction has occurred , and the flight should b
term inated as soon as practicable.
I l l u m i nation of the low voltage annunciator and ammeter
d ischarge i ndications may occur d u ring low RPM conditions
with an electrical load on the system , s uch as d u ring a low
RPM taxi. U nder these conditions, the l ig ht will go o ut at
h ig her RPM.
C I R C U IT B R EAKERS A N D FUSES
All circuit breakers i ns ide the ai rplane are of the "push to reset"
or "switch/breaker" type. The power distribution module uses spade
type (automotive style) fuses and one glass type fuse (controlling
the clock) .
Spare fuses for the power distribution module are located i ns ide
the module. If one of the spare fuses is used , a replacement spare
should be obtained and rei nstal led before th e next flight.

Revision 4

AI RPLA N E
annu nciator extinguishes,
N OTE
&
SYSTE MS DESC R I PTION
normal
SECTION
l
1 0 �
alternato
I
7-35