Piper COMANCHE PA-24-180 Service Manual page 548

PIPER COMANCHE
SERVICE MANUAL
e. Cycle the
genertor:
Method 1 - Move voltmeter lead from "BAT" to "GEN" terminal of reulator.
Retard p~-
erator speed until generat
voltage is reduced to 4 volts. Move voltmeter lead back to "BAT"
terminal of regulator. Bring enertor beck to specified speed, and noe volta
setting.
Method 2 - Connect a variable resistance into the field circuit, a in Figure 9-7. Turn out
all resistance.
Operate generator at specified sped.
Slowly increase (tur in) resitance
until
generator voltage is reduced to 4 volts. Turn out all resistace
again, and note voltage setting
(with voltmeter connected as in Figure 97). Regulator cover must be in place.
f. Note the thermometer reading and select the Normal Rnge of Voltage for this temperature
as listed in specifications paragrph 941.
g. Note the voltmeter reading with reulator cover in piece.
h. To adjust voltage setting turn adjusting screw (Figure 9-6). Turn clockwise to increase
setting and counterwise to decrease voltage setting.
CAUTION
If adjusting screw is turned down (clockwie) beyond ran
, spring
support may not return when screw is backed off. In such case,tum
screw couner-clockwise
until there is ample clearance between
screw hed and spring support. Then bend spring support up care-
fully until it touches the screw head. Final setting of the unit
should always be made by increasing spring tension, never by re-
ducing it. If setting is too high adjust unit below required value
and then raise to exact setting by increasing the spring tension.
After each adjustment and before taking reading replace the regu-
lator cover and cycle the generator.
Variable Resistance Method-
a. Connect ammeter and V ohm variable resistor in series with the battery as shown in Figure
9-8.
NOTE
It is very important that the variable resistance be connected at the
"BAT" terminal as shown in Figure 9-7 rather than at the "GEN"
terminal, even though these terminals are in the same circuit. An
examination of the wiring diagram. Figure 93, will show that rep-
lation begins at the point where the shunt windings are connected
to the series circuit. Any small resistance added to the circuit be*
tween the generator and this point will simply be offset by a rise in
generator voltage without affecungthe output shown at the ammeter.
b. Connect voltmeter between "BAT"
terminal and ground.
c. Place thermometerwithin inch of regulator cover to measure regulator ambient temperature.
d. Operate generator at specified speed. Adjust variable resistor until current flow is 8-10
amperes. If less current than is required above is flowing it will be necessary to turn on aircraft
lights to permit increased generator output. Variable resistance can then be used to decrease
ELECTRICAL SYSTEM
ISSUED: /11/72
3 B2