Piper Navajo Chieftain PA-31-350 Service Manual page 634

NAVAJO CHIEFTAIN SERVICE MANUAL
e. Shutdown the system, including the master electrical switch. Connect a portable voltmeter
(non-precision) such as Simpson No. 260 or equivalent between the "FIELD" terminals of the left and right
regulators in addition to the aircraft system wires already on these terminals. The positive terminal of the
meter is to be on the right regulator terminal. Use a 30-volt or 50-volt meter range initially.
f. Restore operation of the right engine and alternator system using load and RPM as in Step d, and
turn on the left alternator system switching. (HOWEVER, THE LEFT ENGINE IS NOT OPERATING.)
g. Now slowly rotate the left regulator voltage adjustment while observing the voltmeter connected
between the field terminals. If a reverse (downscale) reading is obtained with meter polarity as specified,
turning the "LEFT" regulator adjustment counterclockwise will bring the meter up scale. Then slowly set the
"LEFT" adjustment to a point where the voltmeter will read a low value. Any reading from zero to 8.0 volts is
acceptable. A stable reading should not be expected. A lower meter range such as 10-volts may be used for this
adjustment. Now reconnect the wire to join the "PAR" terminals of the two regulators and observe that the
voltmeter drops to a very low value (0.2 to 0.5-volt) and it will be stable. Continue operations in this manner for
5 to 10 minutes to establish initial warmup of the "LEFT" regulator and alternator system. After the warmup
period make a final adjustment of the balance. This is done by again briefly opening the "PAR" circuit between
regulators and touching up the "LEFT" adjustment for a low reading of the voltmeter between field terminals.
Again any value from zero to 8.0-volts is acceptable; and again it will not be stable while the "PAR" circuit is
open. Remove the adjustment screwdriver and replace the snap plug in the "LEFT" regulator adjustment hole.
h. Shutdown the "RIGHT" engine and master switch. Remove all voltmeter leads. Reconnect the
"PAR" circuit wire removed in Step b and check all terminal screws for security.
INTENTIONALLY LEFT BLANK
Reissued: 9/23/80
ELECTRICAL SYSTEM
3D8