This solves it.
http://www.advancedcustomfields.com/resources/acf-fields-relationship-query/
function my_relationship_query( $args, $field, $post ) {
// get posts for current logged in user
$args['author'] = get_current_user_id();
return $args;
}
add_filter('acf/fields/relationship/query/key=<field_key>', 'my_relationship_query', 10, 3);