using meta_query to query a custom field using OR

I wouldlike to run the folowing but also have it retun a post if the job refernce maches the keyword search using OR but i cannot get it to work:

if($jobtype != '') $filtertype[] =  array('taxonomy' => 'jobtype','terms' => $jobtype,'field' => 'slug');

		if($location != '') $filters[] = array('key' => '_job_location','compare' => 'LIKE','value' => $location);
		if($industry != '') $filters[] = array('key' => '_job_industry','compare' => 'LIKE','value' => $industry);

		if($salary_per != '' && $salary_per != 'all') $filters[] = array('key' => '_job_salary_per','compare' => 'LIKE', 'value' => $salary_per);
		if($salary_from != '') $filters[] = array('key' => '_job_salary_from','compare' => '>=','value' => $salary_from, 'type' => 'NUMERIC');
		if($salary_to != '') $filters[] = array('key' => '_job_salary_to','compare' => '<=','value' => $salary_to, 'type' => 'NUMERIC');

	    if($kewords != '') $filters['relation'] = 'OR';
		if($kewords != '') $filters[] = array('key' => '_job_ref','compare' => 'LIKE', 'value' => $kewords);

		$args = array(
      'post_type' => $post_type,
      //"$tax" => $tax_term->slug,
      'post_status' => 'publish',
      'posts_per_page' => $postperpage,
	  'orderby' => 'date',
	  'paged' => $paged,
	  'order' => $order,
      'meta_query' => $filters,
	  'tax_query' => $filtertype,
      's' => $kewords);

THis works if i search for a word in the content of anythihg but if i type in a job reference it doesn bring back any posts. I assume it is not searchign in the custom field _job_ref.

How can i enable it to search in the custom field as well?

This is the parts i added of the custom field:

if($kewords != '') $filters['relation'] = 'OR';
		if($kewords != '') $filters[] = array('key' => '_job_ref','compare' => 'LIKE', 'value' => $kewords);