My air con 36000btu under ceiling carrier is blowing air which is not cold but the temperature is set on 17 degrees

Did you have a routine maintenance check before using this unit? Did you check the coolant level with the proper gauges? What is your temperature outside, AND inside? Is this the first usage, or an event that just surfaced?

You start with a routine visual check of this unit for coolant leaks inside and out, preferably by a tech.