DorianGrave

I solved in this way.
I created a new search form with this code :

<form action="/" method="get">
  <fieldset>
        <input type="text" name="s" id="search" value="" style="width:85%"/>
         </fieldset>
<input type="hidden" name="post_type[]" value="custom_post_name" />
<input type="hidden" name="post_type[]" value="custom_post_name" />
<input type="hidden" name="post_type[]" value="custom_post_name" />
<input type="hidden" name="post_type[]" value="custom_post_name" />
</form>

Same for the other search form who has “post_type[]” value=”post” instead custom types.