Guys/gals,

I'm wiring up a relay (without a protection diode). Does polarity matter when I connect the coil wires?

I'm wondering if maybe the electromagnet is pushing towards the wrong way. It's a 5 pin relay and my normally closed connection isn't opening when I apply power to the coil. The normally closed connection I have is pin 30 to 87a. I have wired up power to one side of the coil and a switched ground to the other side.

 

Coil polarity doesn't matter unless it has a snubber diode.

Is the relay just switched battery power? If it is connected to anything like sensors, ecu, cpu or something like that you need one with a diode. When the relay deactivates it creates a little AC pulse that can damage some stuff.

 

Thanks, jjwalker.

Found the problem and why the relay was buzzing. I was getting power for the coil from the same wire that the relay was supposed to open the connection to. This wire was going to a load that I wanted on the NC side of the relay when not energized. When I grounded the switch on the other side of the coil, the relay would cut off the load, killing the load, but also the relay coil side. So the load would connect, relay energize...cause relay switch to disconnect, and around like this in a vicious circle.

Simple mistake, but had me confused. Note: Pic. below shows how NOT to wire a normally closed load.