Your air conditioner blows hot air?

Answer 1

It most likely is low on refrigerant and needs to be recharges. It could be an electrical or mechanical problem, as well.

Another reason could be choking of the radiator cooling coils which blow hot air out from the back of your AC. This generally happens if the external part of your room AC is situated around potential choking materials lying loose such as waste, birds feathers etc. The radiator fan sucks such loose material into the radiator coils which get choked, resulting in back-flow of hot air of the radiator into your room. It also adversely affects the cooling cycle as the gas does not get cooled adequately, in the radiator.