Rc on manpower supply

You mean ST on works contract (includes service as well as replacement of parts)? If yes, partial reverse charge is applicable. Service provider is required to pay 50% of ST and the service receiver to pay balance 50% on reverse charge basis.

My q is on Manpower Supply, not on Work Contract

But your query is regarding repair of AC/machinery etc which clearly falls under the definition of works contract (if service and goods are involved). If you mean manpower supply, then service recipient is required to pay 100% ST on reverse charge basis provided the service is provided by an individual/HUF/Firm/AOP, located in a taxable territory to a business entity registered as body corporate located in a taxable territory.

In Work Contract Service Material + Labour are required, but in Manpower Supply only service is required.

in my query we are only receiving repair service, not goods purchased. That,s why 100% RC would be levied

Service of AC/machinery does not fall under the category of manpower supply. For definition of manpower supply: /forum/analysis-of-reverse-charge-mechanism-for-manpower-supply-services-or-security-services-328869.asp

In your case, it is just service of machinery etc without involvement of goods. Hence no reverse charge is applicable for the service recipient. However, service provider is required to levy ST if no exemption is applicable.