Why is my air conditioning leaking in my car?

It's water condensing from your air conditioner unit and leaking out of the unit onto your floor. There should be a small rubber hose connected to the bottom of your heater box to route this water out of the car. It's either plugged up or disconnected. Look under the car just behind the firewall and see if you can locate the hose. Run a stiff piece of wire up inside and see if you can free the blockage.