HEXA

ELECTRICAL 327 CHECKING RELAYS: 1. By using a relay, a heavy current can be turned on and off by a switch using much less current. For example, in the circuit shown here, when the switch is turned on ( closed ), current flows to the coil of the relay. Then, its contact is turned on ( closed ) and the light comes on. The current flowing through the switch is much less than that for the light. 2. Relays may be classified as the normally open- type or the normally closed-type, depending on their contact construction. NOTE The De-energized state means that no current is flowing through the coil. The energized state means that current is flowing through the coil. (a)The normally open-type When a normally open relay as illustrated here is checked, there should be no continuity between terminals 30 and 87 when the relay is de-energized. There should be continuity between terminals 30 and 87 when battery voltage and ground are applied to terminals 85 and 86. The relay condition is determined by this check. NOTE Check the relay in both condition, i.e. energized and not energized (b)The normally closed-type When a normally closed relay as illustrated here is checked, there should be continuity between terminals 30 and 87 when the relay is de-energized. There should be no continuity between terminals 30 and 87 when battery voltage and ground are applied to terminals 85 and 86. The relay condition is determined by this check. NOTE Check the relay in both conditions, i.e. energized and not energized.