My air conditioner makes a strange noise after it has turned from "fan" to "low cool". The noise is as if the a/c has difficulty in cooling. And it does not cool. The noise stops for a while and repeats again.
What can be the cause of this noise and not cooling?
Please help me with this matter.
Thank you and much appreciated your help in advance.

Are you talking about the outside fan? There is a number of reasons it's not colling. If the outside fan is not working properly this would cause no cooling.