If you want a cheap and dirty way to check and you have the gauges out
of the car, take two AA batteries and stack them up like you do in a
flashlight, take 2 wires that both ends are stripped on and run some
electrical tape around them so you have a wire fastened to the + side
and a wire fastened to the - side. Hook the + to the plus terminal on the
gauge and the minus to the - or ground side of the gauge. Give it a few
seconds and you should see the needle moving.