Piper Arrow IV Turbo Maintenance Manual page 226

6. The voltage regulator heat sink, or case, is the ground connection for the electronic circuit. Therefore,
if this unit is tested on the bench it is most important that a wire, No. 14, be connected between the regulator
case and the alternator. If the regulator does not regulate between 13.6 and 14.4-volts, one of the following
conditions may exist:
A. Regulates, but out of specification. The regulator is out of calibration and must be replaced.
B. The voltmeter continues to read battery voltage.
(1) Poor or open connections within the wiring harness.
(2) The regulator is "open."
C. Voltage continues to rise.
(1) Regulator housing not grounded.
(2) Regulator shorted, must be replaced.
7. These are some of the things to look for in case of failure:
A. Poor or loose connections.
B. Poor ground on the regulator housing.
C. Shorted alternator windings.
D. A grounded yellow wire. (This will cause instantaneous failure.)
E. Disconnecting the regulator while the circuit energized.
F. Open circuit operation of the alternator. (The battery disconnected.)
OVER VOLTAGE RELAY. (Wico)
CHECKING OVER VOLTAGE RELAY.
The relay may be tested with the use of a good quality, accurate voltmeter, with a scale of at least 20-volts
and a suitable power supply, with an output of at least 20-volts, or sufficient batteries with a voltage divider to
regulate voltage. The test equipment may be connected by the following procedure:
1. B+ is connected to "Bat" of the over-voltage control.
2. B- is connected to the frame of the over-voltage control.
3. Be sure both connections are secure, and connected to a clean, bright surface.
4. Connect the positive lead of the voltmeter to the "Bat" terminal of the over-voltage control.
5. Connect the negative lead of the voltmeter to the frame of the over-voltage control.
6. The over-voltage control is set to operate between 16.2-volts to 17.3-volts. By adjusting the voltage,
an audible "click" may be heard when the relay operates.
7. If the over-voltage control does not operate between 16.2 and 17.3-volts it must be replaced.
AMMETER.
The ammeter is mounted in the instrument panel. This instrument measures the output of the alternator into
the entire electrical system including the battery charging demand.
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL
1J10
24-37-00
Page 24-39
December 1, 1978