Checking Relay - Piper PA-24 Comanche Service Manual

PIPER COMANCHE SERVICE MANl"AL
• terminal is connected to the regulator "POS" terminal. The circuit trace will be burned open between points
F-F. Figure 9<!(,.
IMPORTA'\T
For further assistance. follow the procedure in
Delco-Remy
Sen-ice
Bullet in
IR-273
when troubleshooting circuits containing this
regulator.
.9-60. Relay,
(Delco-Remy)
9~61.
Checking Relay. The relay 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
predetermined value. When the circuit opens. the alternator voltage will be eliminated. The relay is designed
so that the battery will continue to hold the relay contacts open until the engine is stopped ort he
rnaster sw
itch
is opened. The '\0. 1 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 removed from the aircraft. an electrical check can be made on a test bench
to
determine
if
the relay
is
operating properly.
•
CAUTIO:"
REL.AY
•
VARIABLE
____.. RESISTOR
VOLTMETER
BATTERIES
FIGl'RE 9-27. RELAY TESTS
Do not remove the cover and attempt
to
make adjustments on this relay. If the
assembly does not pass the following
electrical check. discard the relay. If the
relay does pass the following electrical
check. it may be re-used.
a. Turn to the "open" or maximum resistance posi-
tion a 100 ohm variable resistor having a wattage rating of
III:-
watts or above.
b. Connect this resistor with a voltmeter and
two
12
volt batteries in series to the relay 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. Slowlv decrease the resistance and observe the
maximum voltmeter reading obtained. This read ing 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.
ISSl'ED: 8/18/72
3B19
ELECTRICAL SYSTE;\1