Multiple ajax call

While calling multiple ajax call in a page sometimes ajax call do not take place for that we need to place the  below code before ajax call

$.ajaxSetup ({ 

        cache: false 

    });

Example:

$.ajaxSetup ({ 

        cache: false 

    });

    $('#city_id').change(function(){

        $('#weatherreport').html('".$Loadingimage."').load('".$vUrl."?id='+this.value+'&ajax=1');

        return false;

    });