PIPER AIRCRAFT, INC.
PA-28-161, WARRIOR III
MAINTENANCE MANUAL
2E8
24-30-00
PAGE 16
Nov 30/06
CHART 4 (Sheet 3 of 3)
TROUBLESHOOTING STANDBY ALTERNATOR REGULATOR (BC203-2D)
Trouble Cause Remedy
C. If the measurements in Steps A and B are satisfactory, prepare to monitor the voltage between
terminals 3 and 7 of the regulator with the engine running. Move the aircraft to a safe location for a
2000 RPM runup. Start the engine. Minimize the bus loads and bring the engine RPM up to
approximately 2000. Switch OFF the primary alternator. Wait for the STBY ALT ON annunciator to
illuminate. At light bus loads this could take a minute or two. Note the voltage between terminals 3
and 7 of the regulator and begin switching ON additional bus load. The monitored voltage should
increase at the rate of 0.056 Volts for each Amp of standby alternator load.
(1) If the voltage does not change, verify standby alternator output with the ship’s ammeter or a
clamp-on ammeter probe. If the standby output is verified and there is still no change in the
monitored voltage, suspect a bad current sensor.
(2) If the voltage decreases instead of increasing, the 10 Ga. current sensor wire is connected
backward. Reverse the connection and re-run the test.
(3) If the voltage increases at approximately the correct rate, continue adding load until the
voltage is greater than 6.2 volts. At or above this voltage, the lamp should be flashing. If not
suspect a bad regulator.
10. Intermittent problems are the hardest to find. Temporarily bring small test wires into the cockpit from 2 or
3 points in question to allow monitoring them with the DVM during periods of system failure. Double
check all screw terminals for security. Try a 5 pound pull test on all crimp joints and make sure that the
terminal is crimped on the wire, not the insulation.
11. Noise problems are also difficult to find. A few tips to help with curing noise problems follow:
A. A unitized grounding system helps prevent noise problems by preventing voltage differences
between different ground points.
B. The battery acts as a noise filter in the system. Poor connections to the battery or a battery that is
going bad can add to or even cause noise problems.
C. Shielding of low level audio leads (especially microphone leads or headset leads) is required.
Sometimes the shields in the cables can separate from repeated flexing. Try checking shield
continuity with an ohmmeter or substituting another headset, microphone, etc.
D. Wire routing may be important in some installations. Separation of noise carrying conductors such
as P leads from other wiring may help. Running noisy wiring parallel to other wiring in the same
bundle is asking for trouble. Wires at 90 degrees to one another, however, do not couple noise.
E. Running transmitter feed lines close to and in parallel with other wiring can cause a problem.
Normally, problems will only be encountered if there is a mismatch and therefore a high SWR in the
antenna system. If noise or charging system breaker tripping occurs during Comm transmit only or
when the transponder is ON only, check the corresponding antenna system carefully or separate
the transmission line from other wiring.
F. The best plan is to stop the noise at its source. Once the noise is loose, it can be difficult to filter it
out of all affected systems. Try to locate the offending item and correct the problem at that point.
Switching off the alternator, the mags (first one then the other), or any other electrical equipment
that generates noise should help to find the offender.
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