if you attach a test light to the sending unit, coolant one is easiest, it should blink.

at the gauge you should see the same thing with the key on of course.

you can verify the gauge with 2 AA batteries in series to make 3 volts.
attach those to the gauge posts and it should move to the middle.

I used a battery charger to test the vr once. instead of wiring it to a battery. you should see the output blink using a test light as well.