PIPER AIRCRAFT, INC.
PA-28-161, WARRIOR III
MAINTENANCE MANUAL
2E6
24-30-00
PAGE 14
Nov 30/06
CHART 4 (Sheet 1 of 3) (PIR-BC203-2D-trouble.wpd, Rev. C.)
TROUBLESHOOTING STANDBY ALTERNATOR REGULATOR (BC203-2D)
Trouble Cause Remedy
Following this procedure will locate the most common system problems encountered. When calling for
additional factory support, the information gained from these checks should be readily available to aid
your Piper Dealer’s Service Advisor in narrowing the field of possibilities as quickly as possible. Record
the various measurements in the spaces indicated.
Refer to the electrical schematics in 91-24-30 and a high impedance (preferably digital) volt/ohmmeter
(DVM) to make the following checks.
1. Setup
A. Ensure the engine is not running,
B. The magnetos are OFF, and
C. That no external power is applied to the aircraft electrical system.
2. Turn all switches off. Use the lowest resistance scale on the DVM. Check resistance between the battery
negative (-) terminal and both Terminal 7 of the regulator and the engine case. Measurements over 0.5
Ohm to either would be cause for investigation. In this case, check the engine ground strap, battery
ground strap, and regulator ground wire for loose or contaminated connections, broken conductors or
bad crimp joints. If these measurements are less than 0.5 Ohm, any of these three points may be used
as reference (-) for the following measurements.
A. Resistance from battery to Terminal 7: _________Ohms.
B. Resistance from battery to engine case: _________Ohms.
3. Turn on the battery master and alternator field switches. Measure the voltage on the battery bus and on
Terminal 1 of the regulator. The voltages should be equal within 0.2 volts. A difference of greater than 0.2
volts may be caused by using a breaker as the source for Terminal 1 that supplies another device of
considerable load. Change to a lightly loaded breaker or a breaker dedicated to Terminal 1 and the low
voltage lamp. It is recommended that Terminal 1 not be jumped to Terminal 6. If Terminal 1 has no
voltage, the regulator will not operate.
A. Bus voltage: __________ volts.
B. Terminal 1 voltage: ___________volts.
4. Measure the voltage on Terminal 6 of the regulator. It should be within 0.5 volts of the bus voltage. A
difference of greater than 0.5 volts may be caused by poor contacts in the field breaker or field switch,
poor crimp joints, or loose screw terminals in the wiring between the bus and Terminal 6. Absence of
voltage on Terminal 6 will prevent the regulator from operating.
Terminal 6 voltage:____________volts.
5. Check the voltage on Terminal 5 of the regulator. The voltage should be between 13 and 15 volts. A
voltage outside this range may indicate a bad regulator.
Terminal 5 voltage:___________volts.
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