Whenever you find your air conditioner leaking water out onto the floor, the very first suspicion would be problem with the drain pan or the drain pipe coming out of the drain pan.
A photo of an air conditioner drain pan looks like this below:
To explain how water is formed inside an air conditioner, we will try to understand the cooling process one by one. When you turn on your air conditioner, it draws in the hot humid air from your rooms, passes this hot air through an evaporator coil inside your A/C. This evaporator coil contains a refrigerant which absorbs the heat and transfer the heat out onto the compressor located outside your house backyard usually.
During this cooling process, water vapor is formed on the surface of the evaporator coil. This water then drips along the coils onto the draining pan below the evaporator coil. A water drain hose is connected to the edge of this drain pan and water is drained out through this drain hose.
Sometimes this drain hose can be blocked due to dirt and grime or algae. You need to use a small brush to insert into this drain hose and clean the inside of the hose. You may also use vinegar or cleaning agent to clean the inside of the drain hose. Some people put their mouth onto one end of the drain hose and blow very hard to cause the dirt and blockage to clear into the drain.
Another method is if you know how, you can open up the middle portion of your furnace containing the air conditioner and take a look at the drain pan inside. At times, there are dirt, grime or wooden bits pieces lodged onto the surface of the drain pan. This prevents the water from properly reaching the drain hose connector. So instead the water have no where else to go, except to drip out of the sides of the drain pan. Remove and clean those clogged stuff on your drain pan and you should be okay.
In my case, it was the problem with clogged draining pan. Also my drain pan for whatever reason was tilted slightly on one side, causing water to drip out of the drain pan on that side. Cleaning the drain pan properly and balancing the drain pan in a straight angle, solved the air conditioner water leak problem for me.
Try the above mentioned method and see if that solves the problem. You might save some money instead of calling a professional repair guy to fix it for you. Calling a professional Air conditioning repair guy could be your last resort. Of course, if you don't have time on your hand to fix the air conditioner, then go ahead and call a professional repairman.
Some air conditioner professional would recommend you change your entire air conditioning unit when you really don't need to. Watch out for such professional guy, they could be scaring you further with nonsense tactics.