Piper Navajo PA-31 Service Manual page 735

372
REGULATOR
TEST VOLTMETER
Figure 11-34. Testing Regulator (Prestolite)
d. The regulator under test is to be mounted on a grounded metallic surface using three
No. 8 screws pulled up tight. For extended test periods the heat transfer from regulator to
the mounting surface is significant.
e. A ground wire between the regulator "GND" terminal and the aircraft or test stand
structure is essential for proper operation. The alternator frame must also be solidly bonded
to the system ground.
f. The alternator does not need to be polarized; therefore, never connect ground, even
momentarily, to either the regulator field terminal or to the alternator field terminals. Do
not interchange I and F leads to regulator as this will destroy the regulator.
g. The LAMAR regulator is intended for use with alternator systems having one field
terminal grounded at the alternator. The other field terminal F2 of the alternator is
connected to the
"FIELD" terminal of the regulator.
NEVER UNDER ANY
CIRCUMSTANCE PERMIT A GROUND TO CONTACT THIS CIRCUIT EVEN FOR AN
INSTANT WHILE POWER IS APPLIED TO THE SYSTEM. Due to this precaution, the
mechanic should not use tools near these circuits while power is applied.
h. The alternator should be in good condition and capable of producing full output,
and the alternator drive belt must be adjusted tight enough to prevent slippage.
i. The battery must be in good condition and should be fully charged.
j. The voltmeter and ammeter should be of the best quality and should be accurate.
k. A carbon-pile connected across the battery may be used to load the charging circuit
while testing the regulator.
11-48. TESTING REGULATOR (PRESTOLITE).
a. The procedure for testing the regulator, whether on the airplane or on the test
bench, remains the same. Connect test meters as shown in Figure 11-34.
b. All circuit connections should be clean and tight. This includes the test instrument
connections which must not come loose or open the charging circuit at any time while the
system is operating.
c. The voltmeter will not indicate the true regulator setting until the regulator has been
operating in the charging system or on the test bench for at least one minute, at a charge
rate of from 10 to
15-amperes.
Reissued: 10/12/79
ELECTRICAL SYSTEM
PIPER NAVAJO SERVICE MANUAL
4C9