Use Views for Search
I was looking for an answer for hours... I thought I made a mistake, but it seems there is a bug in the Views module! I guess I'm not the only one with this problem, so I'd like to share the sollution I finally found.

Make a custom module and add these lines of code:

function mymodulename_views_query_alter(&amp;$view, &amp;$query) {
  // Fix bug where multiple terms in search index filter returns no results
  if (isset($query-&gt;relationships['search_total'])
      &amp;&amp; !empty($query-&gt;fields['score'])
      &amp;&amp; empty($query-&gt;fields['score']['table'])) {
    $query-&gt;fields['score']['table'] = 'search_total';
  }
}


The sollution was found here: https://drupal.org/node/1948510