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Relay question

805 Views 2 Replies 3 Participants Last post by  Rick_L
On a NO relay does it matter which side of the control is +12 and which side is ground(contacts 85 & 86)You would think that either way the switch would close when +12v is applied.

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On a NO only relay it doesn't matter about 30 and 87, but if you have a DT (double throw) with a NC contact it does, so it's a good idea to always use 30 for power and 87 for the device.
Likewise, on most relays, it doesn't matter if 85 or 86 is ground, BUT, if you happen to install a relay with diode spike suppression, then 85 has to be power and 86 has to be ground.
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