police will help you if the person had told you like. Never buy ac(s) from houses or individuals who claim warranty/ service etc. Once you bought, the deal is over. If the ac fails immediately after the purchase you cant blame them. Its your risk.

But in this case you can say, you bought because he gave full assurance, its in good condition and all service. Sure, you can lodge a complaint and be sure there is witness for the deal and his promise.