Piper Navajo PA-31 Service Manual page 736

373 2
ALT
DC
CARBON
AMMETER
PILE
PAR FIELD
REGULATOR
UNDER TEST
5
GND BUS
PRECISION
1/2WW PRESS-TO-TEST
BATTERY
V/M
NORMALLY OPEN
Figure 11-35. Testing Regulator (Lamar)
d. Connect the voltmeter and the ammeter as shown in Figure 11-34. Start the engine
and adjust its speed to obtain 3,000 to 4,000 alternator RPM. Turn on accessories as needed
to establish 10 to 15-ampere electrical load, or use a carbon-pile across the battery to obtain
this charge rate.
e. After one minute operating time, check the regulator operating voltage as indicated
by the voltmeter. Refer to Alternator Service Test Specifications, Paragraph 11-36, for the
correct operating voltage. The operating voltage is shown for the ambient temperature in
which the regulator is operating.
f. If the voltmeter reading indicates that the operating voltage is not within limits, lift
the plastic plug from top of regulator and adjust the voltage to the desired value. Replace
the plug after adjustment. Before condemning the regulator, recheck the alternator and the
battery; making sure that they are in good condition. Recheck all circuit connections and all
wiring for unwanted resistance (voltage drop test). Recheck the voltmeter for accuracy and
repeat the entire operating test.
11-49. TESTING REGULATOR (LAMAR).
a. The procedure for testing the regulator, whether on the airplane or on the test
bench, remains the same. Connect the test meters and regulator wiring as shown in Figure
11-35.
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 five minutes, at a charge
rate of from 10 to 15-amperes.
d. With the connections made as shown in Figure 11-35, start the engine and adjust its
speed to obtain an RPM of 1500. Adjust the carbon pile or accessory load to establish the
Reissued: 10/12/79
ELECTRICAL SYSTEM
PIPER NAVAJO SERVICE MANUAL
4C10