Circuit Breakers And Fuses; Ground Service Plug Receptacle - Cessna 150 AEROBAT A150M Pilot Operating Handbook

SECTION 7
AIRPLANE & SYSTEMS DESCRIPTIONS
OVER-VOLTAGE SENSOR AND WARNING LIGHT
CESSNA
MODEL Al50M
The airplane is equipped with an automatic over-voltage protection
system consisting of an over-voltage sensor behind the instrument panel
and a red warning light, labeled HIGH VOLTAGE, under the ammeter.
In the event an over-voltage condition occurs, the over-voltage sen-
sor automatically removes alternator field current and shuts down the al-
ternator. The red warning light will then turn on, indicating to the pilot
that the alternator is not operating and the battery is supplying all electri-
cal power.
The over-voltage sensor may be reset by turning the master switch
off and back on again. If the warning light does not illuminate, normal al-
ternator charging has resumed; however, if the light does illuminate again,
a malfunction has occurred, and the flight should be terminated as soon
as practical.
The warning light may be tested by momentarily turning off the ALT
portion of the master switch and leaving the BAT portion turned on.
CIRCUIT BREAKERS AND FUSES
Most of the electrical circuits in the airplane are protected by "push-
to-reset" circuit breakers mounted under the engine controls on the in-
strument panel. Exceptions to this are the battery contactor closing (ex-
ternal power) circuit, clock, and flight hour recorder circuits which have
fuses mounted near the battery. Also, the cigar lighter and control wheel
map light are both protected by circuit breakers on the instrument panel,
and fuses behind the panel. An automatic-reset type circuit breaker, be-
hind the instrument panel, protects the alternator field and circuitry.
GROUND SERVICE PLUG RECEPTACLE
A ground service plug receptacle may be installed to permit the use
of an external power source for cold weather starting and during lengthy
maintenance work on the electrical and electronic equipment. The recep-
tacle is located behind a door on the left side of the fuselage near the aft
edge of the cowling.
Just before connecting an external power source (generator type or
battery cart), the master switch should be turned ON. This is especially
important since it will enable the battery to absorb transient voltages
which otherwise might damage the transistors in the electronic equipment.
The battery and external power circuits have been designed to com-
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