Piper Comanche PA-24 Service Manual page 695

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PIPER COMANCHE SERVICE MANUAL
terminal is connected to the regulator "POS" terminal The circuit trace will
be
burned open between points
F-F. Figure 9-26
For further assistance. follow the procedure in Delco-Remy Se,,·ice
Bulletin I
R-27~
when troubleshooting circuits containing this
regulator
9-60.
ReIB~.
(Delco-RemI)
9-61. Checking Relay. The relav is a protective device against high voltage that may appear in the electrical
system. The relay will open the circuit to the alternator field winding if the system voltage should ever reach a
pred"'ermined \alue. When the circuit opens. the alternator voltage will be eliminated. The
rela~
is designed
so : the battery will continue to hold the
rela~·
contacts open until the engine is stopped or the master '" itch
is ollened. The '0. I terminal on the relay is connected to the master switch. and the '\0 2 terminal to the
regulator "POS" terminal. For connections. refer to the aircraft wiring diagram.
With the relay remo\ed from the alrcrafl. an electrical check can be made on a test bench to determine ir
the relay is operating
properl~
REU.Y
VARIABLE
RESISTOR
VOLTMETER
BATTERIES
FIGURE 9-27. RELAY TESTS
ISSUED: 8/18/72
Do not remove the cover and attempt to
make adjustments on this relay. If the
assem bly does not pass the following
electrical check. discard the relay. If the
relay does pass the following electrical
check. it
ma~
be re-used
a. Turn to the "open" or maximum resistance posi-
tion a 100 ohm variable resistor having a wattage rating of
II;' watts or above.
b Connect this resistor with a voltmeter and t"o 12
volt batteries in senes to the
rela~
as shown in Figure 9-27
Connect the negative battery post to the relay base. and the
positive battery· post to the variable resistor.
c. Slowly decrease the resistance and obse"e the
maximum voltmeter reading obtained. This reading will
be the voltage at which the contacts open.
d. The contacts should open at 16-18 volts. If they
do not. discard the relay.
3B19
ELECTRICAL SYSTEM