How do I extend front end search function?

I have a client that would like customers to be able to search by product code (I have made the product code the model number). When I try searching a product code from the front end it comes up with nothing. I'm assuming the search function is only related to the product name.

Does any one have any idea how I can include the model number in the search?

Any questions please don't hesitate to ask.

Cheers!

I need to do the same thing, but have it also include the Attributes in the search. I've just posted a topic here http://forum.opencart.com/viewtopic.php?f=20&t=46010