Take an IVR and ground it's housing to the negative of the you 12v power source.
Then after determining which terminal is the 12v in connect that to the positive of your 12v power source.
Hook a small 12v bulb to the output terminal and the negative terminal on your power source you should see the bulb flash on and off .
Just a note...
I was a firm believer of oem parts. So I kept my OEM thermal electric IVR and fried my fuel gauge when it failed closed and fed 12v to my gauges.
I now have a RTE IVR and will never look back