CESSNA SECTION 3
MODEL 152 EMERGENCY PROCEDURES
1 July 1978 3-15
Electronic components in the electrical system can be adversely affected by higher than
normal voltage. The alternator control unit includes an over-voltage sensor that normally will
automatically shut down the alternator if the charge voltage reaches approximately 31.5 volts.
If the over-voltage sensor malfunctions or is improperly adjusted, as evidenced by an
excessive rate of charge shown on the ammeter, the alternator should be turned off,
nonessential electrical equipment turned off and the flight terminated as soon as practical.
INSUFFICIENT RATE OF CHARGE
NOTE
Illumination of the low-voltage light and ammeter discharge
indications may occur during low RPM conditions with an electrical
load on the system, such as during a low RPM taxi. Under these
conditions, the light will go out at higher RPM. The master switch
need not be recycled since an over-voltage condition has not
occurred to de-activate the alternator system.
If the over-voltage sensor should shut down the alternator, a discharge rate will be shown on
the ammeter followed by illumination of the low voltage warning light. Since this may be a
"nuisance" trip-out, an attempt should be made to reactivate the alternator system. To do this,
turn the radios off, then turn both sides of the master switch off and then on again. If the
problem no longer exists, normal alternator charging will resume and the low-voltage light will
go off. The radios may then be turned back on. If the light illuminates again, a malfunction is
confirmed. In this event, the flight should be terminated and/or the current drain on the battery
minimized because the battery can supply the electrical system for only a limited period of
time. If the emergency occurs at night, power must be conserved for later use of the landing
light and flaps during landing.
To Next Page
