WordPress default search feature basically sucks. If you think that I’m wrong just give it a try… Done? Happy with the results? Most probable answer is “No, I’m not!”. This is a true headache for any client that needs a decent search feature.
The thing is that the search works relatively well with posts and pages, but you will have trouble with Custom Post Types, Custom Taxonomies and Custom Fields. Basically, everything that is not the title or content of a page or post will not be searched.
The solution? Well, actually it is really easy to enhance the search feature with the help of this great plugin: Search Everything by Zemanta. The good news? It is free and regularly updated so it is a true find for every WordPress installation. Let me just get your attention to this: after activating the plugin make sure that under Options>Search Everything. On this section I would suggest that you activate at least these options: Search every tag name, Search custom taxonomies, Search every category name and description, Search every excerpt and Search every custom field.
As always, if you have any suggestion or simply a better solution please let me know using the comment section just below.