Leaking central a/c unit

All central A/C units have a condensate drain line that comes from just under the evaporator in the Main air supply plenum.

You may have a blockage in that drain line and will have to remove the pipe to clear the obstruction. Try flushing the drain pipe with warm water until it flows easily from the top to the end.

You might have a gravity drain that goes into a floor drain or a french drain along the basement walls. The other typical drain installation is a condensate pump that the water drains into and when the float in the tank is lifted, a small pump turns on and pumps the water (condensate) out of the house either thru a drain hose thru the wall, or into a drain in the basement, etc.

Check the entire drain line and anything connected to it for any possible obstructions and/or blockage.

If you have any other questions once you take a look at your installation, just add a comment and I'll check back within a day to provide more info, based on your input.

I hope you found this very helpful and best regards!