When creating models, you need to place the file in application/models/ and name the file in all lowercase – like logon_model.php
The logon_model.php should contain the following:
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
class Logon_model extends CI_Model
{
public function __construct()
{
parent::__construct();
}
...
Now, what you can do, to test if your application model is reachable, is to try opening it in the browser – like so:
http://example.org/application/models/logon_model.php
If you see the text No direct script access allowed it means you hit the right file (if you are in doubt, try writing something else in the exit() in the first line).
Secondly, for loading the model in your controllers, you should be able to do like this:
public function index()
{
$this->load->model('logon_model');
...
}
If everything above checks out as expected I would begin looking at file permissions and/or possibly symlinks if you are using any.