11
55
1414
1313
99
IllustIllustration 6-5. ration 6-5. SPSP, ST 10 amp Relay, ST 10 amp Relay
When the relay is energized, the coil shifts theWhen the relay is energized, the coil shifts the
switch, connecting pins (9 and 5) and pins (12 andswitch, connecting pins (9 and 5) and pins (12 and
8) completing the circuit of both sets of pins.8) completing the circuit of both sets of pins.
When the L.E.D. is illuminated, the coil of the relayWhen the L.E.D. is illuminated, the coil of the relay
is energizis energized. ed. This does not indiThis does not indicate that the con-cate that the con-
tact points of the internal switches are functioningtact points of the internal switches are functioning
properlyproperly. . Do not rely on the L.E.DDo not rely on the L.E.D. to give the full. to give the full
operational status of the relay.operational status of the relay.
The most effective way to troubleshoot this typeThe most effective way to troubleshoot this type
relay is witrelay is with an ohmmeterh an ohmmeter. . This can be accom-This can be accom-
plished by removing the wires at relay socket ter-plished by removing the wires at relay socket ter-
minals (12, 8, and 4) and terminals (9, 5, and 1).minals (12, 8, and 4) and terminals (9, 5, and 1).
In a de-energized state, ensure that terminals (9In a de-energized state, ensure that terminals (9
and 1) and terminals (12 and 4) have continuityand 1) and terminals (12 and 4) have continuity
between them. between them. With an ohmmWith an ohmmetereter, check the, check the
resistance between terminals (9 and 1) and termi-resistance between terminals (9 and 1) and termi-
nals (12 and 4)nals (12 and 4). . The ohmmetThe ohmmeter should inder should indicate aicate a
readireading of 0 - ng of 0 - 40 ohms. 40 ohms. EnerEnergizgize the relay ande the relay and
check the resistance between terminals (9 and 5)check the resistance between terminals (9 and 5)
and terminaland terminals (12 and 8). s (12 and 8). The ohmmetThe ohmmeter shoulder should
indiindicatcate a e a readireading of 0 ng of 0 - 40 ohms. - 40 ohms. If thesIf these twoe two
checchecks are goodks are good, the relay is go, the relay is good. od. If one ofIf one of
these checks fails and 12 VDC required at termi-these checks fails and 12 VDC required at termi-
nal 14 was or was not present, or ground signal atnal 14 was or was not present, or ground signal at
terminal 13 was or was not present, dependant onterminal 13 was or was not present, dependant on
the desired state of relay (energized or de-ener-the desired state of relay (energized or de-ener-
gized), the relay is bad and must be replaced.gized), the relay is bad and must be replaced.
88
55
44
11
99
1212
1414
1313
IllusIllustration 6-6. tration 6-6. DPDP, DT 10 amp Relay, DT 10 amp Relay
Double-Pole, Double-Throw 15 amp RelaysDouble-Pole, Double-Throw 15 amp Relays
(Illustration 6-7)(Illustration 6-7).. A relay is nothing more than anA relay is nothing more than an
electrielectrically contrcally controlled switcolled switch. h. Relays are alwaysRelays are always
shown on electrical circuits in a de-energizedshown on electrical circuits in a de-energized
state. state. The positivThe positive side of the relay coie side of the relay coil is pin 14l is pin 14
whiwhile the negativle the negative side of the coil is pin 13. e side of the coil is pin 13. EithEitherer
signal, 12 VDC or ground (or both), can be sent tosignal, 12 VDC or ground (or both), can be sent to
the relay coil to energize the relay.the relay coil to energize the relay.
When the relay is de-energized, the internalWhen the relay is de-energized, the internal
switch connects pins (9 and 1) and pins (12 andswitch connects pins (9 and 1) and pins (12 and
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