Codeigniter by adding ".html" after controller name

I do not know why when I try to make a ajax call to the url " link " I get a 404 error saying the following " The url link "was not found on the server (404). I can not find where the ".html" that he is adding after the controller name comes from, the application is running perfectly on another server.

I do not know where the problem comes from, but I'll post the .htaccess to see if it is an error in it:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]

And this is the thread that makes the request:

var controller = 'login';
            var base_url = '<?php echo base_url();?>';

            function validaLogin() {

                $.ajax({
                    'url' : base_url + controller + '/ax_validaLogin',
                    'type' : 'POST', //the way you want to send data to your URL
                    'data' : {'username': document.getElementById('username').value,
                              'senha'  : document.getElementById('senha').value
                             },
                    'success' : function(data){ //probably this request will return anything, it'll be put in var "data"
                        var container = $('#errorMessage'); //jquery selector (get element by id)

                        if(data == "sucesso") {
                            window.location.href='home';
                        }
                        else {
                            if(data){
                                container.html(data);
                                $("#erroLogin").show();
                                focusLogin();
                            }
                        }
                    }
                });
            }   

Remembering that I'm using Codeigniter 2, PHP5.6 and Apache2 on Linux Mint 18.