How to exclude a field when a search is done? I just enable the Search Form (provide by the search module) block to allow the visitor to make searches.

When a search is done the entered word is searched in all field of the nodes.  

Can I exclude a field?

Let's say the content type has the fields: title, body and provider.

Then when a search is done I need to exclude the field provider from the search.

I have the custom_search module enabled but I see no way to exclude fields.
Default Search is not customizable. Consider using one of more advanced solutions:


Search API with client module that will suit your needs.
Finder with proper views configuration.