Sorry about the delay. I have found something that might help. You will need to modify one file though.
1. Go to wp-content/plugins/ajax-search-pro/includes/search_content.class.php and open that file.
2. Replace the file contents with this: http://pastebin.com/raw.php?i=YHAsD3ZA
3. Open up the General options -> Behaviour panel and change the “Keyword Logic” option to AND. (https://i.imgur.com/Q9SGAGa.png)
After saving the options the characters without accents should work as well.
I hope it will work!Best,
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