So I'm trying to help my ant hook up a new thermostat. To tell you the truth I don't know the brand of it. All I know is that it has R C W Y G I only have R W Y G wires coming out. I think I need one more wire to connect to the T'stat for the display to come on since its powere by 24v ac. Do I need to bring a wire from commond of transformer to C on T'stat?

I think so.