[John Fields]

This fix is for 4.0.17.
I have seen a few posts on this but I think due to my crapness I could not get it working. These fixes have been from a couple of posts so I will just do a quick recap how I got it working for me.

First of all find the file /include/search.php

Replace:

if (!empty($data["by_fulldescr"])) {
			if($current_area == 'C' || $current_area == 'P') {
				$condition[] = "IF($sql_tbl[products_lng].full_descr IS NOT NULL AND $sql_tbl[products_lng].full_descr != '', $sql_tbl[products_lng].full_descr, $sql_tbl[products].fulldescr) LIKE '%".$data["substring"]."%'";
			} else {
				$condition[] = "$sql_tbl[products].fulldescr LIKE '%".$data["substring"]."%'";
			}
		}

With:

if (!empty($data["by_fulldescr"])) {
         if($current_area == 'C' || $current_area == 'P') {
            $condition[] = "IF($sql_tbl[products_lng].full_descr IS NOT NULL AND $sql_tbl[products_lng].full_descr != '', $sql_tbl[products_lng].full_descr, $sql_tbl[products].fulldescr) LIKE '%".$data["substring"]."%'";
         if (!empty($data["by_productcode"])){
               $condition[] = "$sql_tbl[products].productcode LIKE '%".$data["substring"]."%'";
            if(!empty($active_modules['Product_Options'])) {
               $condition[] = "$sql_tbl[variants].productcode LIKE '%".$data["substring"]."%'";
            }
         }
         } else {
            $condition[] = "$sql_tbl[products].fulldescr LIKE '%".$data["substring"]."%'";
         }
      } 

Right now that is done find the file /skin1/customer/search.tpl

This is for the little search box in the topbar (if thats where you have it)

Replace this:

<FORM method="POST" action="search.php" name="productsearchform">
<INPUT type="hidden" name="mode" value="search">
<INPUT type="hidden" name="posted_data[by_title]" value="Y">
<INPUT type="hidden" name="posted_data[by_shortdescr]" value="Y">
<INPUT type="hidden" name="posted_data[by_fulldescr]" value="Y">

With this:

<FORM method="POST" action="search.php" name="productsearchform">
<INPUT type="hidden" name="simple_search" value="Y">
<INPUT type="hidden" name="mode" value="search">
<INPUT type="hidden" name="posted_data[by_title]" value="N">
<INPUT type="hidden" name="posted_data[by_shortdescr]" value="N">
<INPUT type="hidden" name="posted_data[by_fulldescr]" value="N">
<INPUT type="hidden" name="posted_data[by_productcode]" value="N">

Okay now this is the tricky part. Doing the following changes will make the Advanced Search section work.

Look for the file /skin1/customer/main/search_result.tpl

First of all change this:

<FORM name="searchform" action="search.php" method="POST">

For this (make sure you add the new line):

<FORM name="productsearchform" action="search.php" method="POST">
<INPUT type="hidden" name="mode" value="search">

And finally replace this:

<TD width="5"><INPUT type="checkbox" name="posted_data[by_title]"{if $search_prefilled eq "" or $search_prefilled.by_title} checked{/if}></TD><TD nowrap>{$lng.lbl_title}</TD>
<TD width="5"><INPUT type="checkbox" name="posted_data[by_shortdescr]"{if $search_prefilled eq "" or $search_prefilled.by_shortdescr} checked{/if}></TD><TD nowrap>{$lng.lbl_short_description}</TD>
<TD width="5"><INPUT type="checkbox" name="posted_data[by_fulldescr]"{if $search_prefilled eq "" or $search_prefilled.by_fulldescr} checked{/if}></TD><TD nowrap>{$lng.lbl_det_description}</TD>

With this:

<TD width="5"><INPUT type="checkbox" name="posted_data[by_title]"{if $search_prefilled eq "" or $search_prefilled.by_title} checked{/if}></TD><TD nowrap>{$lng.lbl_title}</TD>
<TD width="5"><INPUT type="checkbox" name="posted_data[by_shortdescr]"{if $search_prefilled eq "" or $search_prefilled.by_shortdescr} checked{/if}></TD><TD nowrap>{$lng.lbl_short_description}</TD>
<TD width="5"><INPUT type="checkbox" name="posted_data[by_fulldescr]"{if $search_prefilled eq "" or $search_prefilled.by_fulldescr} checked{/if}></TD><TD nowrap>{$lng.lbl_det_description}</TD>
<TD width="5"><INPUT type="checkbox" name="posted_data[by_productcode]"{if $search_prefilled eq "" or $search_prefilled.by_productcode} checked{/if}></TD><TD nowrap>Product Code</TD>

Hopefully that should get things running smoothly, it works for me anyhow.
Please dont berate me if there is a full comprehensive solution to this problem, the search function on this forum is much like the xcart search function.............turd.