I have a multimeter. To test for incoming power, I’m assuming I need to remove relay and test where pins are inserted. Correct?
Just so you have a better idea...
Think of a relay as an electrically actuated switch for a higher current circuit. A low-power switched line, such as a headlight switch, can be used to energize a higher current circuit for halogen headlights. (A headlight circuit is used as an example for simplicity).
With no power, the normally closed (NC) #87A is connected to the common terminal #30.
When the coil across pins 85 & 86 is energized with 12VDC to actuate the relay, the common terminal #30 is switched to the normally open (NO) #87.
Keep in mind that sometimes the engineering is not that straight forward and often pin 85 will be permanently energized with 12VDC (with respect to ground) and another circuit or device will apply a ground to pin 86 to energize the relay. In this instance, with the relay installed in the circuit, you may measure 12VDC on both sides of the coil, this condition will not energize the relay.
Also, keep in mind that often there is no standard as to which side of the coil receives the 12VDC. The relay coil has no polarity, either terminal can be connected to 12VDC or ground.
Hopefully, this explanation provides more clarity than confusion.
Please feel free to ask any questions.
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