My air-conditioner is possessed!!!!!!! Help!!? I have a pane a/c unit specifically only in the order of...

I have a pane a/c unit specifically only in the order of 9 months old. For awhile presently, whenever I turn it OFF, it makes this strange popping sound for around a minute. Anyone have any impression what that could be?
Better draw contained by my fireplace?
Answers:    It's like 10 degree in Chicago today and this one is complaining almost her air conditioner.
Mildew remover?
it is getting cold, and the metal moves