A/C water leak inside car

What causes water on the floor of a car?

The evaporator water drain is an integral part of the evaporator housing assembly. A crack or break in the housing may reduce the cooling capacity of the air conditioner.

Engine hot air leak inside hvac box. 

If the case has a crack or break on the engine side of the firewall, excessive engine heat may enter the case and thereby reduce the efficiency of the air conditioning system.

How do you unclog a car AC drain line?

If the evaporator (water) drain becomes clogged, it is easily cleaned with a stiff wire from the outlet in; care should be taken not to puncture the delicate evaporator core.