You can connect the side of the gauge that goes to the sensor to ground momentarily. Needle will stay still for a short time and then move rapidly. Remove the short to ground when you notice movement. Don't hold it there for a long time or you can damage the guage. I have a little power supply that I use to test clusters, but any 12Volt source will do.
You can buy a AA battery holder at Radio Shack for a few bucks. Buy the one that holds 3 AA batteries and that will give you 4.5vDC which should peg or almost peg the gauge. Should be good for a quick field test.