Testing Regulator (Lamar) - Piper Navajo Chieftain PA-31-350 Service Manual

37 3
DC
CARBON
AMMETER
PILE
PRECISION
1/2W
PRESS -TO-TEST
BATTERY
V/M
2,200 OHM
NORMALLY OPEN
Figure 11-19. Testing Regulator (Lamar)
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 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.
g.
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.
h.
The battery must be in good condition and should be fully charged.
i.
The voltmeter and ammeter should be of the best quality and should be accurate.
j.
A carbon-pile connected across the battery may be used to load the charging circuit while testing
the regulator.
11-23. 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 11-19.
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 11-19, start the engine and adjust its speed to
obtain an RPM of 1500. Adjust the carbon pile or accessory load to establish the 10 to 15 ampere load
value. Note that the battery charge current is indicated by the ammeter. Therefore, the current value may
change downward at the beginning of a test run. This will be especially true if the battery was used for
engine starting.
Reissued: 9/23/80
ELECTRICAL SYSTEM
Reissued: 9/23/80
NAVAJO CHIEFTAIN SERVICE MANUAL
3D6