Overcharging Problems?

Okay, so I tried the connection from the ignition part to the regulator to the pos of the battery and had gotten no change. All it did was go back down to 12.3 volts, connect the plug again and it jumps back up to 14.9-15.2. I don't understand, when the fans come on it goes down to like 13.1 and when the lights are on (with the fans running) it goes down further 12.5...also, I had tried this with a new regulator I had just bought today.