Cirrus DESIGN SR20 Information Manual page 297

Cirrus Design
SR20
Section 3 - Emergency Procedures
Alternator Failure
Abnormal ammeter indications and illumination of the ALT FAIL
caution light(s) and/or illumination of the LOW VOLTS warning light
may indicate electrical power supply system malfunctions. A broken
alternator drive belt, wiring fault or a defective alternator control unit is
most likely the cause of the alternator failure. Usually, electrical power
malfunctions are accompanied by an excessive battery rate of charge
or a battery discharge rate.
During low RPM conditions with a heavy electrical load, such
as during low-speed taxi, illumination of the LOW VOLTS
warning light, illumination of one or both ALT FAIL caution
lights, and/or battery discharge ammeter indications can
occur. Normally, these indications will return to normal as
RPM is increased.
ALT FAIL Light Illuminated
1. Ammeter Select Switch.................................SELECT FAILED ALT
2. If Amps = 0, Failed ALT Master Switch ........... CYCLE (OFF – ON)
3. If Amps remain = 0, Failed ALT Master Switch ........................ OFF
4. Failed Alternator Circuit Breaker ............................................ PULL
Battery Excessive Rate of Charge
After starting engine and heavy electrical use at low RPM, the battery
will be low enough to accept above normal charging. However, the
ammeter should be indicating less than two needle widths of charging
current after thirty minutes of cruising flight. If the charging rate
remains above this rate, the battery could overheat and evaporate the
electrolyte.
Additionally, electronic components can be damaged by an
overvoltage. Normally, each alternator's ACU over-voltage sensor
automatically opens the affected alternator's circuit breaker and shuts
down the alternator if the voltage reaches approximately 31.8 volts. If
the over-voltage sensor fails, perform the following checklist:
P/N 11934-S10
Original: 09-28-99
• Note •
Section 9
Supplements
3 of 10