How to use AJAX for an exposed filter form of a Views block?
You must install the Better Exposed Filters module:


  What else can I do with BEF?
  
  
  Add help text for each exposed filter
  Tame long lists with scrollable checkbox/radio button lists or select all/none links
  Provide instant feedback by updating the View using AJAX whenever an exposed filter is changed
  Use the jQuery Slider widget for greater-than, less-than or in-between types of filters
  


You can read more about this in Views exposed filters without &quot;Apply&quot; button