Custom search block that searches by content type not working

I think this has been fixed in Custom Search 7.x-1.17. Can you try this version?
See #2297015: Path generated for apache solr filters doesn't resolve.
In general, always try with the latest (or dev) version available before reporting a bug.

Strange, the commit hasn't been taken. I've just re-pushed it to dev.
See http://cgit.drupalcode.org/custom_search/commit/?id=42188d0

Is it working now? It still doesn't seem to work for me. The query passed to Solr doesn't contain filter query for bundles. In the latest release version 7.x-1.18, fq is used instead of f. Here is the code:

function _custom_search_apachesolr_search($variables, &$keys, $fields) {
  // Use the search info for the apachesolr module to get the search path.
  $solr_info = apachesolr_search_search_info();
  $type = 'search/' . $solr_info['path'] . '/' . $variables['keywords'];
  $keys = array();

  if (count($variables['types']) && !in_array('all', $variables['types'])) {
    foreach ($variables['types'] as $t) {
      $keys['fq[' . count($keys) . ']'] = 'bundle:' . $t;
    }
  }

  if (module_exists('taxonomy') && count($variables['terms'])) {
    // Get all fields info to get correct filter names.
    $taxonomy_fields = array();
    foreach ($fields as $name => $settings) {
      if ($settings['type'] == 'taxonomy_term_reference') {
        $voc = taxonomy_vocabulary_machine_name_load($settings['settings']['allowed_values'][0]['vocabulary']);
        $taxonomy_fields[$voc->vid] = $name;
      }
    }
    // Build keys for taxonomy.
    foreach ($variables['terms'] as $t) {
      $vocid = taxonomy_term_load($t)->vid;
      $keys['fq[' . count($keys) . ']'] = 'im_' . $taxonomy_fields[$vocid] . ':' . $t;
    }
  }

  foreach (module_implements('custom_search_apachesolr_processing') as $module) {
    $function = $module . '_custom_search_apachesolr_processing';
    
    if (function_exists($function)) {
      call_user_func_array($function, array(&$keys, $fields, $variables['other']));
    }
  }
  return array('path' => $type, 'query' => $keys);
}

I just figured it out myself. It's not because of custom_search but a setting in Apachesolr module that prevents manual faceting passed thru the URL. Enabling it and the bundles are passed to Solr successfully. However, is there any way to use "OR" operator for the bundles? For example, I want to search nodes of either "page" or "event" content type. Currently, bundles seem to be "AND"ed.

I'm not used to Solr so let me know (or provide a patch) how the query should be modified to have OR, and I'll do my best to implement that.

@jdanthinne: Currently, we're having something like this: fq[0]=bundle:event&fq[1]=bundle:page, which will result in "AND" to be used. For "OR", it would be like this instead: fq[0]=bundle:(event OR page).

Can you try this patch and tell me if it's what you need?

I waste my whole day to figure out this, but end of the day it's just a checkbox tic :) thanks @ngocketit