Well the problem was caused by chewing of wires by rat.
First the SA told me the motor has gone, and has to be replaced.
He said that the vehicles is of 08 model, and not covered under warranty.
and gave extended warranty booklet into his hands.
Then he told that he will replace it under warranty.
But later he told me that wires were chewed by rat.
And they changed the wire set & now its working fine.
Now my worry is what would they have said if i didn't had extended warranty.
They might have told that they had replaced the motor & i would have paid for it.
In the mean time refrigerant was topped up, now AC is cooling fast.
With a complimentary wash.