Electrical Failures; Electrical Overload - Piper Dakota PA-28-236 Pilot Operating Handbook

SECTION 3
EMERGENCY PROCEDURES

3.17 ELECTRICAL FAILURES

Loss of alternator output is detected through zero reading on the ammeter.
Before executing the following procedure, insure that the reading is zero and not
merely low by actuating an electrically powered device, such as the landing light.
If no increase in the ammeter reading is noted, alternator failure can be assumed.
The electrical load should be reduced as much as possible. Check the
alternator circuit breakers for a popped circuit.
The next step is to attempt to reset the overvoltage relay. This is
accomplished by moving the ALT switch to OFF for one second and then to ON.
If the trouble was caused by a momentary overvoltage condition (16.5 volts and
up) this procedure should return the ammeter to a normal reading.
If the ammeter continues to indicate "0" output, or if the alternator will not
remain reset, turn off the ALT switch, maintain minimum electrical load and
land as soon as practical. All electrical load is being supplied by the battery.
3.18 ELECTRICAL OVERLOAD (Alternator over 20 amps above known
electrical load)
If abnormally high alternator output is observed (more than 20 amps above
known electrical load for the operating conditions) it may be caused by a low
battery, a battery fault or other abnormal electrical load. If the cause is a low
battery, the indication should begin to decrease toward normal within 5 minutes.
If the overload condition persists attempt to reduce the load by turning off
nonessential equipment. For airplanes with interlocked BAT and ALT switch
operation, when the electrical load cannot be reduced turn the ALT switch
OFF and land as soon as practical. The battery is the only remaining source of
electrical power. Also anticipate complete electrical failure.
For airplanes with separate BAT and ALT switch operations, turn the BAT
switch OFF and the ammeter should decrease. Turn the BAT switch ON and
continue to monitor the ammeter. If the alternator output does not decrease
within 5 minutes, turn the BAT switch OFF and land as soon as practical. All
electrical loads are being supplied by the alternator.
REPORT: VB-910
3-14
PIPER AIRCRAFT CORPORATION
ISSUED: JUNE 1, 1978
REVISED: FEBRUARY 2, 1981
PA-28-236, DAKOTA