Can you please tell me is the compressor is ruining or not. OK answering the questions from the possibilities.The common Problem of ac's are given below you can check for that.
If the compressor is not ruining then can check the capacitor and the Voltages coming in the machine.
2. Refrigerant Leak
Refrigerant leak might be the reason.
3. Sensors failure.
Some times the failure of senors and the electrical board is cause to the air conditioner not blowing cold air.
Reasons and the Solution why Central air Conditioner fails