My air conditioner just started making a loud banging noise. I have central air and the noise is coming from inside the house where the A coil is located. There is a lot of water under the coil. I turned it off. What do you think may be causing the noise? Actually, I just turned it back on and it sounds more like a loud grinding noise.

Sounds like it may have iced up, some of the ice may have dropped into the furnace or air handler and the fan hitting it.

The reasons for an air conditioning unit to freeze up are many, lack of air flow (dirty filter) belt slipping, registers closed in house, low on refrigerant and also if the thermostat is set to low (below 70) if can freeze up, only the last will solve itself if turned off for a while. I hope this is helpful. Mike