The difference between an air conditioner and a dehumidifier is not all that great. An air conditioner, like a dehumidifier, pulls warm moist air over its cold coils. The difference is that an air conditioner does not reheat the air before exhausting it into your home.
What you get is nice cold air blowing out of the air conditioning unit. It also doesn’t have a humidistat, so when the home reaches a preset temperature the AC will shut down, even though your home may still have high humidity. But more importantly, depending on when you turn on the air conditioner, it may do more harm than good.
For example the temperature in your flooded home is 74⁰ degrees Fahrenheit and the relative humidity (RH) is 90%. You turn on the air conditioning system hoping that you will cause faster drying to occur. What really happens is that the cool air coming out of your ducts reaches the room's dew point, which for the above conditions is about 70⁰ degrees. Within minutes condensation begins to form and basically, it begins to rain in your flooded areas. Not much drying going on, is there?
So it is best to use a dehumidifier, and not an air conditioner, to help dry out your home. The dehumidifier’s job is solely to remove humidity. There are times when an air conditioning system can help if conditions are right, like to control the heat build-up caused by the dehumidifier. But this should be left up to a water damage restoration professional who has the ability to monitor your home’s environment to determine when it is the best time to turn on and off the AC unit.
but the usefulness of each can be quite different in given situations.