Overvoltage Relay Operational Check - Piper APACHE PA-23-235 Service Manual

PIPER AZTEC SERVICE MANUAL
b. 28 volt system: Relay contacts open between 31.5 and 32.5 volts. Use 36 volts to test.
NOTE
These units are not adjustable. Replace the overvoltage control
if it does not test to specifications.
11-100. OVERVOLTAGE RELAY OPERATIONAL CHECK. This check should be made
at each 500 hour inspection, per the following instructions:
a. Determine that aircraft master switch is OFF.
b. Pull out (OFF) all circuit breakers except the main and auxiliary voltage regulators( 10
amp).
c. Turn off the right and left alternator output circuit breaker switches (90 amp).
d. Set the voltage regulator to MAIN.
e. Obtain a variable D.C. voltage power supply and set it to zero output.
f.
Connect the power supply to the aircraft through the external power receptacle.
NOTE
On aircraft without an external power receptacle, disconnect
the battery cables and connect the power supply to the cables.
CAUTION
Connections must be positive to positive and negative to
negative.
g. Obtain a volt/ohmmeter and set the selector to a D.C. voltage scale of no less than 16.5
volts. Connect the meter VOM lead to the output (REG.) terminal of the MAIN overvoltage
relay. Connect the meter COM lead to the airframe ground.
h. Increase the output voltage of the variable D.C. power supply until the MAIN
overvoltage relay trips out. When the relay operates, the VOM needle should drop to zero
volts. Record the power supply voltmeter reading which was indicated just prior to the
overvoltage relay operating. Voltage limits are: Min. 15.5-volts - Max. 16.5-volts for the 14-
volt system and Min. 31.5-volts - Max. 32-5-volts for the 28-volt system.
CAUTION
Limit overvoltage operation to two minutes maximum.
i. Reduce the power supply voltage to zero.
j. Set the VOM to resistance scale and determine continuity between battery terminal
(BAT) and regulator terminal (REG.) on the overvoltage relay, to insure that the relay is reset.
k. Change the voltage regulator selector switch from MAIN to AUX. Reconnect the
volt/ohmmeter to the AUX overvoltage relay and repeat steps i thru 1.
1. Reset circuit breakers, turn on alternator output circuit breakers, reset voltage
regulator selector to MAIN, disconnect VOM, and reconnect the battery cables if previously
removed.
ELECTRICAL SYSTEM
Reissued: 2/18/81
4F10